Just when you thought it was safe to put green paint around the edges of your CDs without ridicule, there's yet another CD tweak that's sure to bring howls of laughter from the skeptics: cryogenically freezing CDs. They won't be laughing for long, however, when they hear for themselves the sonic results of this process.
Ed Meitner, designer of the Museatex line of electronics, has discovered that cryogenically freezing a CD changes the physical structure of polycarbonate, the plastic material from which CDs are made. The result is reportedly an audible improvement in sound quality. In this process, CDs are placed in a cryogenic freezing chamber and the temperature is slowly reduced over eight hours to 75 Kelvins, or about -300 degrees Fahrenheit. This is approximately the temperature of liquid nitrogen, the chamber's cooling agent. The temperature is then slowly brought back to room temperature over another eight hours.
This technique reportedly relaxes the lattice structure of a material (polycarbonate in the case of CD) that has been previously distorted by heat or pressure, both of which are present during CD injection molding. By reducing the molecular bonds holding the material together, the internal stress in the material is reduced, thus changing its resonant characteristics. Indeed, a treated disc feels slightly more flexible than an untreated disc.
But how could freezing a CD possibly affect its sound quality? So what if the polycarbonate has a different structure? The data are all ones and zeros. Furthermore, uncorrected data errors are almost nonexistent in most discsci without treatment, ruling out improved data integrity as an answer. I posed these questions to Ed Meitner and got the following explanation (footnote 1).
Mechanical vibration of the disc causes the HF signal to become noisy and have excessive jitter. The HF signal is the raw signal output from the CD player's photodetector (footnote 2). By freezing a CD, the disc's mechanical resonance is lowered, improving the quality of the HF signal retrieved from the disc. Although theory states that noise and jitter in the HF signal will have no effect on sound quality—the HF signal is squared, buffered, decoded, filtered, and clocked out of another buffer with quartz-crystal accuracy—many digital designers maintain that HF signal quality does affect the sound.
Ed Meitner claims that the HF signal improvement from a cryogenically treated disc is easily measurable. I looked at the HF signal on an oscilloscope from the Esoteric P2 transport with treated and untreated discs. I could see no difference in the signal quality. However, it is very difficult to make comparisons without seeing the two HF signals side by side.
Meitner is talking to some audiophile labels about mass-treating their releases. Apparently, the process is efficient and economical, with the ability to treat thousands of discs at once. Liquid nitrogen, which doesn't come in direct contact with the CDs, is inexpensive and readily available. Interestingly, this process is said to yield similar sonic improvements with a vinyl phonograph record. In addition to CDs and LPs, the process has been used on LaserVision-format video discs, speaker cable, interconnects, integrated circuits, and musical instrument strings.
Cryogenic freezing is also used to treat machine tools like drill bits, copper welding tools, and saw blades. The process reportedly improves their wear characteristics, thus extending the tool's useful life. The treatment doesn't always work, however, and there is no consensus among metallurgists that the process is always beneficial. In fact, the effects of cryogenically freezing materials is not well understood; little scientific research has been done to explain the phenomenon (footnote 3).
Another tweak developed by Ed Meitner is painting a CD's top surface black. This reportedly improves sound quality by improving the signal at the CD player's photodetector. Before describing how this works, let's look at the playback laser beam's path through the disc.
The playback beam enters the disc through the surface without the label. It travels through the 1.2mm disc thickness where it encounters pits impressed in the polycarbonate. To reflect the beam back through the disc and to the photodetector, a thin layer of aluminum is deposited on the disc surface, which conforms to the pit structure. A protective coating of varnish seals in the aluminum and prevents it from oxidizing. The label is then silk-screened on top of the protective coating.
Ed Meitner contends that several mechanisms are at work that degrade the HF signal picked up by the photodetector. One phenomenon is distortion of the aluminum layer by the laser beam's heat. Even though the beam is very low-power—about half a milliwatt—it is focused on such a small area (1.5µm) that the aluminum molecules bend, causing the aluminum layer to flex. This introduces jitter in the HF signal as well as noise in the focus signal.
This phenomenon has reportedly been measured by painting black bars on a CD's top surface (the label side) and looking at various signals. The bar pattern is readily apparent in both the focus servo and HF signals. Painting the CD black reportedly improves the thermal conditions by reducing the contrast in the aluminum molecules caused by laser-induced heat. Another mechanism that is also affected by black paint is the secondary reflection from the disc label. Some laser light passes through the aluminum layer and is reflected to the photodetector by the label. This reportedly causes noise in the HF signal which is manifested as uncertainty in the digital code transitions. Note that the above descriptions are those of Ed Meitner, and have not been independently verified.
How plausible are these explanations? I find some of them hard to believe, especially this last phenomenon. However, there is so much going on in digital audio that we don't know about—especially the optical considerations in data retrieval from CD—that I hesitate to rule out anything (footnote 4).
What really matters is if these treatments work. Since I believe that the ear is the highest-resolution instrument available to explore these phenomena, I gave Ed Meitner three copies of the Stereophile Test CD for treatment. One disc was cryogenically frozen, another was painted black, and the third was both painted and frozen. The Stereophile Test CD is ideal for this purpose: it has a wide variety of music, all recorded by Stereophile contributors. In addition, I know with absolute certainty that the three treated discs as well as my untreated control disc were made by JVC from the same master tape and CD stamper.
I began by listening to my guitar and bass recording from the untreated disc. After switching to the frozen and painted disc, the difference was immediate and obvious. First, the guitar appeared to become louder, with more clarity and detail. Subtle sounds like finger noises and minute instrumental detail jumped forward. The sonic picture became more vivid and immediate. The acoustic bass took on a more rounded character and its musical contribution seemed enhanced. There was a greater degree of air and life around the instruments; they suddenly became more palpable.
The degree to which these characteristics were apparent varied considerably with the type of music. During our annual Stereophile writers' conference in early August, I had an opportunity to play treated and untreated discs for some of the visiting writers. Arnis Balgalvis correctly identified the treated disc in a blind A/B/A comparison when he visited my listening room. He immediately knew that presentation B was different, and his description of the difference was remarkably similar to my impressions.
I repeated the blind test for Peter Mitchell in JA's listening room; Peter also immediately identified the treated disc. In fact, within seconds of hearing the treated disc with the guitar and bass recording, he let out a loud exclamation of surprise. His impressions were consistent with the differences I had heard, which I related to him after the test and his description to me of the differences.
A good point Peter raised was that although there was clearly a difference, he had doubts about which was "better" or more true to the original recording. The treated disc had a brighter, more detailed character that would exacerbate many of CD's problems.
The above listening comparisons were made between an untreated disc and one that was both cryogenically frozen and painted black. Further listening of frozen-only discs and painted-only discs revealed that most of the sonic difference was the result of freezing. The black paint, however, did add to the effect. A second frozen and painted disc sent to me by Museatex had similar differences. However, a look at the disc's inside ring, where the production number is written, revealed that it was a different pressing from my untreated control disc. I would therefore refrain from reaching any conclusions based on this disc. From my experience with the Stereophile Test CD, however, I am convinced that some unexplained phenomena are occurring in frozen and painted CDs.
http://www.stereophile.com/asweseeit/822/index1.html
Wednesday, May 30, 2007
CD: Jitter, Errors & Magic
The promise of "perfect sound forever," successfully foisted on an unwitting public by the Compact Disc's promoters, at first seemed to put an end to the audiophile's inexorable need to tweak a playback system's front end at the point of information retrieval. Several factors contributed to the demise of tweaking during the period when CD players began replacing turntables as the primary front-end signal source. First, the binary nature (ones and zeros) of digital audio would apparently preclude variations in playback sound quality due to imperfections in the recording medium. Second, if CD's sound was indeed "perfect," how could digital tweaking improve on perfection? Finally, CD players and discs presented an enigma to audiophiles accustomed to the more easily understood concept of a stylus wiggling in a phonograph groove. These conditions created a climate in which it was assumed that nothing in the optical and mechanical systems of a CD player could affect digital playback's musicality.
Recently, however, there has been a veritable explosion of interest in all manner of CD tweaks, opening a digital Pandora's box. An avalanche of CD tweak products (and the audiophile's embrace of them) has suddenly appeared in the past few months, Monster Cable's, AudioQuest's, and Euphonic Technology's CD Soundrings notwithstanding. Most of these tweaks would appear to border on voodoo, with no basis in scientific fact. Green marking pens, an automobile interior protectant, and an "optical impedance matching" fluid are just some of the products touted as producing musical nirvana. The popular media has even picked up on this phenomenon, sparked by Sam Tellig's Audio Anarchist column in Vol.13 No.2 describing the sonic benefits of applying Armor All, the automobile treatment, to a CD's surface. Print articles have appeared in the Los Angeles Times, Ice Magazine, and on television stations MTV, VH-1, and CNN, all reporting, with varying degrees of incredulity, the CD tweaking phenomenon.
The intensity of my interest in the subject was heightened by a product called "CD Stoplight," marketed by AudioPrism. CD Stoplight is a green paint applied to the outside edge of a CD (not the disc surface, but the 1.2mm disc thickness) that reportedly improves sound quality. I could not in my wildest imagination see how green paint on the disc edge could change, for better or worse, a CD's sound. However, trusting my ears as the definitive test, I compared treated to untreated discs and was flabbergasted. Soundstage depth increased, mids and highs were smoother with less grain, and the presentation became more musically involving.
Other listeners, to a person, have had similar impressions. Since I am somewhat familiar with the mechanisms by which data are retrieved from a CD (I worked in CD mastering for three years before joining Stereophile), this was perplexing: I could think of no plausible explanation for a difference in sonic quality. As we shall see, the light reflected from a CD striking the photo-detector contains all the information encoded on the disc (footnote 1). Even if CD Stoplight could somehow affect the light striking the photo-detector, how could this change make the soundstage deeper? I was simultaneously disturbed and encouraged by this experience. Disturbed because it illustrates our fundamental lack of understanding of digital audio's mysteries, and encouraged by the promise that identification of previously unexplored phenomena could improve digital audio to the point where today's digital audio era will be regarded as the stone age.
These events prompted me to conduct a scientific examination of several CD "sonic cure-all" devices and treatments. I wanted to find an objective, measurable phenomenon that explains the undeniable musical differences heard by many listeners where, at least according to established digital audio theory, no differences should exist. For this inquiry, I measured several digital-domain performance criteria on untreated CDs, and then on the same CDs treated with various CD tweaks. The parameters measured include data error rates, ability to correct (rather than conceal) data errors, and jitter.
The six CD treatments and devices chosen for this experiment include three that allegedly affect optical phenomena and three that ostensibly affect the CD player's mechanical performance. The three optical treatments tested are CD Stoplight (the green paint), Finyl (a liquid applied to a disc surface, that, according to its promoters, provides "optical impedance matching"), and Armor All. The mechanical devices include CD Soundrings, The Mod Squad's CD Damper disc, and the Arcici LaserBase, a vibration-absorbing CD-player platform. I also measured playback signal jitter in a mid-priced CD player and the $4000 Esoteric P2 transport (regarded as having superb sonics). However, this is not intended as a survey of the musical benefits of these devices and treatments. In addition, I looked at the variation in quality of discs made at various CD manufacturing facilities around the world.
Another purpose of the article is to dispel some common misconceptions about CD error correction and its effect on sonic quality. If one believes the promoters of some of these CD treatments, errors are the single biggest source of sonic degradation in digital audio. In reality, errors are the least of CD's problems. However, this has not prevented marketeers from exploiting the audiophile's errorphobia in an attempt to sell products.
For example, Digital Systems and Solutions, Inc., manufacturer of Finyl, claim in their white paper that error concealment "results in a serious degrading of playback fidelity." They also state that errors can get through undetected, leading to a litany of sonic horrors including: "poor articulation of bass and mid-bass notes, attenuation of dynamics and smearing of transients, increased noise with loss of inner detail and intertransient silence, reduced midrange presence that diminishes clarity and transparency, loss of image specificity and focus, reduction of the apparent width and depth of soundstage—virtually eliminating the possibility of holophonic [sic] imagery, decreased resolution of the low level detail that is so necessary to the recovery of hall ambience, altered instrumental and vocal timbres that lack coherence or cohesiveness, obscuring of vocal textures and expression, instrumental lines and musical themes are more difficult to sort out, complex rhythms and tempos are less easily followed, the music will not be as emotionally involving and satisfying an experience as might have otherwise been possible, subtle breath effects on brass or wind instruments are more difficult to discern as are nuances of fingering and bowing on string instruments." This list, they concede, "is not claimed to be complete."
Technical background
Encoding and data retrieval: Before getting into the measurement results, let's arm ourselves with a little technical background on how the CD works.
A CD's surface is covered by a single spiral track of alternating "pit" and "land" formations. These structures, which encode binary data, are created during the laser mastering process. The CD master disc is a glass substrate coated with a very thin layer of photosensitive material. The glass master is rotated on a turntable while exposed to a laser beam that is modulated (turned on and off) by the digital data we wish to record on the disc. This creates a spiral of exposed and unexposed areas of the disc. When the master is later put under a chemical developing solution, areas of the photosensitive material exposed to the recording laser beam are etched away, creating a pit. Unexposed areas are unaffected by the developing solution and are called lands. These formations, which are among the smallest manufactured structures, are transferred through the manufacturing process to mass-produced discs. Fig.1 is a scanning electron microscope of a CD surface. Note that a human hair is about the width of 50 tracks.
The playback laser beam in the CD player is focused on these tiny pits and held on track by a servo system as the disc rotates. This beam is reflected from the disc to a photo-detector, a device that converts light into voltage. To distinguish between pit and land areas, the pit depth is one-quarter the wavelength of the playback laser beam. When laser light strikes a pit, a portion of the beam is reflected from the surrounding land, while some light is reflected from the pit bottom. Since the portion of light reflected from the pit bottom must travel a longer distance (1/4 wavelength down plus 1/4 wavelength back up), this portion of the beam is delayed by half a wavelength in relation to the beam reflected by the land. When these two beams combine, phase cancellation occurs, resulting in decreased output from the photo-detector. This variable-intensity beam thus contains all the information encoded on the disc.
Now that we understand how the playback beam/photo-detector can distinguish between pit and land, let's look at how these distinctions represent digital audio data. One may intuitively think that it would be logical for a pit to represent binary one and a land to represent binary zero, or vice versa. This method would certainly work, but a much more sophisticated scheme has been devised that is fundamental to the CD. It is called Eight-to-Fourteen Modulation, or EFM.
This encoding system elegantly solves a variety of data-retrieval functions. In EFM encoding, pit and land do not represent binary data directly. Instead, transitions from pit-to-land or land-to-pit represent binary one, while all other surfaces (land or pit bottom) represent binary zero. EFM encoding takes symbols of 8 bits and converts them into unique 14-bit words, creating a pattern in which binary ones are separated by a minimum of two zeros and a maximum of 10 zeros. The bit stream is thus given a specific pattern of ones and zeros that result in nine discrete pit or land lengths on the disc. The shortest pit or land length encodes three bits, while the longest encodes 11 bits. The blocks of 14 bits are linked by three "merging bits," resulting in an encoding ratio of 17:8. At first glance, it may seem odd that EFM encoding, in more than doubling the number of bits to be stored, can actually increase data density. But just this occurs: Storage density is increased by 25% over unmodulated encoding.
EFM has other inherent advantages. By inserting zeros between successive ones, the bandwidth of the signal reflected from the disc is decreased. The data rate from a CD is 4.3218 million bits per second (footnote 2), but the EFM signal has a bandwidth of only 720kHz. In addition, the EFM signal serves as a clock that, among other functions, controls the player's rotational servo.
The signal reflected from the disc is comprised of nine discrete frequencies, corresponding to the nine discrete pit or land lengths (footnote 3). The highest-frequency component, called "I3," is produced by the shortest pit or land length and has a frequency of 720kHz. This represents binary data 100. The lowest-frequency component, called "I11," is produced by the longest pit or land length and has a frequency of 193kHz. This represents binary data 10000000000. The signal reflected from the disc, produced by EFM encoding, is often called the HF (high frequency) signal. The varying periods of the sinewaves correspond to the periods of time required to read the various pit lengths.
At first impression, the HF signal appears to be analog, not one that carries digital data. However, the zero crossings of the waveforms contain the digital information encoded on the disc. Fig.2 shows the relationship between binary data, pit structure, and the recovered HF signal.
Fig.2 Relationship between binary data, pit structure, and the HF signal. (Reproduced from Principles of Digital Audio, Second Edition (1989), by Kenneth C. Pohlmann, with the permission of the publisher, Howard W. Sams & Company.)
HF signal quality is a direct function of pit shape, which in turn is affected by many factors during the CD manufacturing process. There is a direct correlation between error rates and pit shape. Poorly shaped pits result in a low-amplitude HF signal with poorly defined lines. Figs.3 and 4 show an excellent HF signal and a poor HF signal respectively.
CD data errors: Any digital storage medium is prone to data errors, and the CD is no exception. An error occurs when a binary one is mistakenly read as a binary zero (or vice versa), or when the data flow is momentarily interrupted. The latter, more common in CDs, is caused by manufacturing defects, surface scratches, and dirt or other foreign particles on the disc. Fortunately, the CD format incorporates extremely powerful error detection and correction codes that can completely correct a burst error of up to 4000 successive bits. The reconstructed data are identical to what was missing. This is called error correction. If the data loss exceeds the player's ability to correctly replace missing data, the player makes a best-guess estimate of the missing data and inserts this approximation into the data stream. This is called error concealment, or interpolation.
It is important to make the distinction between correction and concealment: correction is perfect and inaudible, while concealment has the potential for a momentary sonic degradation where the interpolation occurs.
A good general indication of disc quality (and the claimed error-reduction effects of some CD tweaks) is the Block Error Rate, or BLER. BLER is the number of blocks per second that contain errant data, before error correction. The raw data stream from a CD (called "channel bits") contains 7350 blocks per second, with a maximum allowable BLER (as specified by Philips) of 220. A disc with a BLER of 100 thus has 100 blocks out of 7350 with errant or missing data. In these experiments, Block Error Rate is the primary indicator of a particular tweak's effect on error-rate performance.
In addition to measuring the effects of CD tweaks on BLER, I explored their potential to reduce interpolations. To do this, I used the Pierre Verany test CD that has intentional dropouts in the spiral track. The disc has a sequence of tracks with increasingly long periods of missing data.
First, I found the track that was just above the threshold of producing an uncorrectable error (called an "E23 error") as analyzed by the Design Science CD Analyzer (see Sidebar). The track was played repeatedly to assure consistency, thus avoiding the ascription to chance of any subsequent change. Then, the same track was played and analyzed, this time after the addition of a CD treatment or device. This twofold approach—measuring a tweak's effect on both BLER and interpolations—would seem to cover the gamut of error-reduction potential.
There are two general misconceptions about CD errors and sound quality: 1) errors are the primary source of sonic degradation; and 2) if there are no uncorrectable errors, there can be no difference in sound.
The first conclusion is largely due to the marketing programs of CD-accessory manufacturers who claim their products reduce error rates. Many of the devices tested claim to improve sound quality by reducing the amount of error concealment performed by the CD player. In fact, interpolations (error concealment) rarely occur. In the unlikely event that concealment is performed, it will be momentary and thus have no effect on the overall sound. At worst, a transient tick or glitch would be audible.
To better understand the nature of data errors, a look at CD Read-Only Memory (CD-ROM) is useful. A CD-ROM is manufactured just like an audio CD, but contains computer data (text, graphics, application software, etc.) instead of music. The data retrieved from a CD-ROM must be absolutely accurate to the bit level, after error correction. If even a single wrong bit gets past the error correction, the entire program could crash. The errant bit may be within instructions for the host computer's microprocessor, causing the whole application to come to an instant halt, making the disc useless.
To prevent this, a quality-control procedure is routinely used at the mastering and pressing facility to assure 100% error-free performance. Samples of the finished CD-ROM are compared, bit for bit, to the original source data. For high-reliability applications, each replicated disc undergoes this process. This rigorous testing reveals much about the error-correction ability of the CD's Cross Interleaved Reed-Solomon encoding (CIRC). Throughout dozens of hours of this verification procedure, I cannot remember even a single instance of one wrong bit getting through.
It could be argued that CD-ROM has additional error-correction ability not found on CD audio discs. This is true, but the additional layer of error correction is almost never invoked. Furthermore, in all the hours of error-rate measuring for this project, I never encountered an E23 error, the first and most sensitive indication of an interpolation (except on the Pierre Verany disc, which has intentional errors). In fact, I saw only one E22 error, the last stage of correction before concealment. In retesting the disc, the E22 error disappeared, indicating it was probably due to a piece of dirt on the disc. Finally, the unlikely occurrence of an uncorrectable error is exemplified by the warning system in the Design Science CD Analyzer. The system beeps and changes the computer's display color to red to alert the operator if even an E22 error (fully corrected) is detected.
http://www.stereophile.com/reference/590jitter/
Recently, however, there has been a veritable explosion of interest in all manner of CD tweaks, opening a digital Pandora's box. An avalanche of CD tweak products (and the audiophile's embrace of them) has suddenly appeared in the past few months, Monster Cable's, AudioQuest's, and Euphonic Technology's CD Soundrings notwithstanding. Most of these tweaks would appear to border on voodoo, with no basis in scientific fact. Green marking pens, an automobile interior protectant, and an "optical impedance matching" fluid are just some of the products touted as producing musical nirvana. The popular media has even picked up on this phenomenon, sparked by Sam Tellig's Audio Anarchist column in Vol.13 No.2 describing the sonic benefits of applying Armor All, the automobile treatment, to a CD's surface. Print articles have appeared in the Los Angeles Times, Ice Magazine, and on television stations MTV, VH-1, and CNN, all reporting, with varying degrees of incredulity, the CD tweaking phenomenon.
The intensity of my interest in the subject was heightened by a product called "CD Stoplight," marketed by AudioPrism. CD Stoplight is a green paint applied to the outside edge of a CD (not the disc surface, but the 1.2mm disc thickness) that reportedly improves sound quality. I could not in my wildest imagination see how green paint on the disc edge could change, for better or worse, a CD's sound. However, trusting my ears as the definitive test, I compared treated to untreated discs and was flabbergasted. Soundstage depth increased, mids and highs were smoother with less grain, and the presentation became more musically involving.
Other listeners, to a person, have had similar impressions. Since I am somewhat familiar with the mechanisms by which data are retrieved from a CD (I worked in CD mastering for three years before joining Stereophile), this was perplexing: I could think of no plausible explanation for a difference in sonic quality. As we shall see, the light reflected from a CD striking the photo-detector contains all the information encoded on the disc (footnote 1). Even if CD Stoplight could somehow affect the light striking the photo-detector, how could this change make the soundstage deeper? I was simultaneously disturbed and encouraged by this experience. Disturbed because it illustrates our fundamental lack of understanding of digital audio's mysteries, and encouraged by the promise that identification of previously unexplored phenomena could improve digital audio to the point where today's digital audio era will be regarded as the stone age.
These events prompted me to conduct a scientific examination of several CD "sonic cure-all" devices and treatments. I wanted to find an objective, measurable phenomenon that explains the undeniable musical differences heard by many listeners where, at least according to established digital audio theory, no differences should exist. For this inquiry, I measured several digital-domain performance criteria on untreated CDs, and then on the same CDs treated with various CD tweaks. The parameters measured include data error rates, ability to correct (rather than conceal) data errors, and jitter.
The six CD treatments and devices chosen for this experiment include three that allegedly affect optical phenomena and three that ostensibly affect the CD player's mechanical performance. The three optical treatments tested are CD Stoplight (the green paint), Finyl (a liquid applied to a disc surface, that, according to its promoters, provides "optical impedance matching"), and Armor All. The mechanical devices include CD Soundrings, The Mod Squad's CD Damper disc, and the Arcici LaserBase, a vibration-absorbing CD-player platform. I also measured playback signal jitter in a mid-priced CD player and the $4000 Esoteric P2 transport (regarded as having superb sonics). However, this is not intended as a survey of the musical benefits of these devices and treatments. In addition, I looked at the variation in quality of discs made at various CD manufacturing facilities around the world.
Another purpose of the article is to dispel some common misconceptions about CD error correction and its effect on sonic quality. If one believes the promoters of some of these CD treatments, errors are the single biggest source of sonic degradation in digital audio. In reality, errors are the least of CD's problems. However, this has not prevented marketeers from exploiting the audiophile's errorphobia in an attempt to sell products.
For example, Digital Systems and Solutions, Inc., manufacturer of Finyl, claim in their white paper that error concealment "results in a serious degrading of playback fidelity." They also state that errors can get through undetected, leading to a litany of sonic horrors including: "poor articulation of bass and mid-bass notes, attenuation of dynamics and smearing of transients, increased noise with loss of inner detail and intertransient silence, reduced midrange presence that diminishes clarity and transparency, loss of image specificity and focus, reduction of the apparent width and depth of soundstage—virtually eliminating the possibility of holophonic [sic] imagery, decreased resolution of the low level detail that is so necessary to the recovery of hall ambience, altered instrumental and vocal timbres that lack coherence or cohesiveness, obscuring of vocal textures and expression, instrumental lines and musical themes are more difficult to sort out, complex rhythms and tempos are less easily followed, the music will not be as emotionally involving and satisfying an experience as might have otherwise been possible, subtle breath effects on brass or wind instruments are more difficult to discern as are nuances of fingering and bowing on string instruments." This list, they concede, "is not claimed to be complete."
Technical background
Encoding and data retrieval: Before getting into the measurement results, let's arm ourselves with a little technical background on how the CD works.
A CD's surface is covered by a single spiral track of alternating "pit" and "land" formations. These structures, which encode binary data, are created during the laser mastering process. The CD master disc is a glass substrate coated with a very thin layer of photosensitive material. The glass master is rotated on a turntable while exposed to a laser beam that is modulated (turned on and off) by the digital data we wish to record on the disc. This creates a spiral of exposed and unexposed areas of the disc. When the master is later put under a chemical developing solution, areas of the photosensitive material exposed to the recording laser beam are etched away, creating a pit. Unexposed areas are unaffected by the developing solution and are called lands. These formations, which are among the smallest manufactured structures, are transferred through the manufacturing process to mass-produced discs. Fig.1 is a scanning electron microscope of a CD surface. Note that a human hair is about the width of 50 tracks.
The playback laser beam in the CD player is focused on these tiny pits and held on track by a servo system as the disc rotates. This beam is reflected from the disc to a photo-detector, a device that converts light into voltage. To distinguish between pit and land areas, the pit depth is one-quarter the wavelength of the playback laser beam. When laser light strikes a pit, a portion of the beam is reflected from the surrounding land, while some light is reflected from the pit bottom. Since the portion of light reflected from the pit bottom must travel a longer distance (1/4 wavelength down plus 1/4 wavelength back up), this portion of the beam is delayed by half a wavelength in relation to the beam reflected by the land. When these two beams combine, phase cancellation occurs, resulting in decreased output from the photo-detector. This variable-intensity beam thus contains all the information encoded on the disc.
Now that we understand how the playback beam/photo-detector can distinguish between pit and land, let's look at how these distinctions represent digital audio data. One may intuitively think that it would be logical for a pit to represent binary one and a land to represent binary zero, or vice versa. This method would certainly work, but a much more sophisticated scheme has been devised that is fundamental to the CD. It is called Eight-to-Fourteen Modulation, or EFM.
This encoding system elegantly solves a variety of data-retrieval functions. In EFM encoding, pit and land do not represent binary data directly. Instead, transitions from pit-to-land or land-to-pit represent binary one, while all other surfaces (land or pit bottom) represent binary zero. EFM encoding takes symbols of 8 bits and converts them into unique 14-bit words, creating a pattern in which binary ones are separated by a minimum of two zeros and a maximum of 10 zeros. The bit stream is thus given a specific pattern of ones and zeros that result in nine discrete pit or land lengths on the disc. The shortest pit or land length encodes three bits, while the longest encodes 11 bits. The blocks of 14 bits are linked by three "merging bits," resulting in an encoding ratio of 17:8. At first glance, it may seem odd that EFM encoding, in more than doubling the number of bits to be stored, can actually increase data density. But just this occurs: Storage density is increased by 25% over unmodulated encoding.
EFM has other inherent advantages. By inserting zeros between successive ones, the bandwidth of the signal reflected from the disc is decreased. The data rate from a CD is 4.3218 million bits per second (footnote 2), but the EFM signal has a bandwidth of only 720kHz. In addition, the EFM signal serves as a clock that, among other functions, controls the player's rotational servo.
The signal reflected from the disc is comprised of nine discrete frequencies, corresponding to the nine discrete pit or land lengths (footnote 3). The highest-frequency component, called "I3," is produced by the shortest pit or land length and has a frequency of 720kHz. This represents binary data 100. The lowest-frequency component, called "I11," is produced by the longest pit or land length and has a frequency of 193kHz. This represents binary data 10000000000. The signal reflected from the disc, produced by EFM encoding, is often called the HF (high frequency) signal. The varying periods of the sinewaves correspond to the periods of time required to read the various pit lengths.
At first impression, the HF signal appears to be analog, not one that carries digital data. However, the zero crossings of the waveforms contain the digital information encoded on the disc. Fig.2 shows the relationship between binary data, pit structure, and the recovered HF signal.
Fig.2 Relationship between binary data, pit structure, and the HF signal. (Reproduced from Principles of Digital Audio, Second Edition (1989), by Kenneth C. Pohlmann, with the permission of the publisher, Howard W. Sams & Company.)
HF signal quality is a direct function of pit shape, which in turn is affected by many factors during the CD manufacturing process. There is a direct correlation between error rates and pit shape. Poorly shaped pits result in a low-amplitude HF signal with poorly defined lines. Figs.3 and 4 show an excellent HF signal and a poor HF signal respectively.
CD data errors: Any digital storage medium is prone to data errors, and the CD is no exception. An error occurs when a binary one is mistakenly read as a binary zero (or vice versa), or when the data flow is momentarily interrupted. The latter, more common in CDs, is caused by manufacturing defects, surface scratches, and dirt or other foreign particles on the disc. Fortunately, the CD format incorporates extremely powerful error detection and correction codes that can completely correct a burst error of up to 4000 successive bits. The reconstructed data are identical to what was missing. This is called error correction. If the data loss exceeds the player's ability to correctly replace missing data, the player makes a best-guess estimate of the missing data and inserts this approximation into the data stream. This is called error concealment, or interpolation.
It is important to make the distinction between correction and concealment: correction is perfect and inaudible, while concealment has the potential for a momentary sonic degradation where the interpolation occurs.
A good general indication of disc quality (and the claimed error-reduction effects of some CD tweaks) is the Block Error Rate, or BLER. BLER is the number of blocks per second that contain errant data, before error correction. The raw data stream from a CD (called "channel bits") contains 7350 blocks per second, with a maximum allowable BLER (as specified by Philips) of 220. A disc with a BLER of 100 thus has 100 blocks out of 7350 with errant or missing data. In these experiments, Block Error Rate is the primary indicator of a particular tweak's effect on error-rate performance.
In addition to measuring the effects of CD tweaks on BLER, I explored their potential to reduce interpolations. To do this, I used the Pierre Verany test CD that has intentional dropouts in the spiral track. The disc has a sequence of tracks with increasingly long periods of missing data.
First, I found the track that was just above the threshold of producing an uncorrectable error (called an "E23 error") as analyzed by the Design Science CD Analyzer (see Sidebar). The track was played repeatedly to assure consistency, thus avoiding the ascription to chance of any subsequent change. Then, the same track was played and analyzed, this time after the addition of a CD treatment or device. This twofold approach—measuring a tweak's effect on both BLER and interpolations—would seem to cover the gamut of error-reduction potential.
There are two general misconceptions about CD errors and sound quality: 1) errors are the primary source of sonic degradation; and 2) if there are no uncorrectable errors, there can be no difference in sound.
The first conclusion is largely due to the marketing programs of CD-accessory manufacturers who claim their products reduce error rates. Many of the devices tested claim to improve sound quality by reducing the amount of error concealment performed by the CD player. In fact, interpolations (error concealment) rarely occur. In the unlikely event that concealment is performed, it will be momentary and thus have no effect on the overall sound. At worst, a transient tick or glitch would be audible.
To better understand the nature of data errors, a look at CD Read-Only Memory (CD-ROM) is useful. A CD-ROM is manufactured just like an audio CD, but contains computer data (text, graphics, application software, etc.) instead of music. The data retrieved from a CD-ROM must be absolutely accurate to the bit level, after error correction. If even a single wrong bit gets past the error correction, the entire program could crash. The errant bit may be within instructions for the host computer's microprocessor, causing the whole application to come to an instant halt, making the disc useless.
To prevent this, a quality-control procedure is routinely used at the mastering and pressing facility to assure 100% error-free performance. Samples of the finished CD-ROM are compared, bit for bit, to the original source data. For high-reliability applications, each replicated disc undergoes this process. This rigorous testing reveals much about the error-correction ability of the CD's Cross Interleaved Reed-Solomon encoding (CIRC). Throughout dozens of hours of this verification procedure, I cannot remember even a single instance of one wrong bit getting through.
It could be argued that CD-ROM has additional error-correction ability not found on CD audio discs. This is true, but the additional layer of error correction is almost never invoked. Furthermore, in all the hours of error-rate measuring for this project, I never encountered an E23 error, the first and most sensitive indication of an interpolation (except on the Pierre Verany disc, which has intentional errors). In fact, I saw only one E22 error, the last stage of correction before concealment. In retesting the disc, the E22 error disappeared, indicating it was probably due to a piece of dirt on the disc. Finally, the unlikely occurrence of an uncorrectable error is exemplified by the warning system in the Design Science CD Analyzer. The system beeps and changes the computer's display color to red to alert the operator if even an E22 error (fully corrected) is detected.
http://www.stereophile.com/reference/590jitter/
The Absolute Sound of What?
One of the things that distinguishes a dedicated audiophile from Joe Q. Public is that he has some notion of what audio fidelity is all about.
The typical buyer of a "steeryo" is seeking nothing more than pleasant or exciting sounds, and is easily satisfied because he has no greater expectation of audio than this. The audiophile, however, is aware that reproduced sound can resemble (more or less) real, live sound, and he is driven in a continual search for that ultimate truth ("fidelity to the original") even while realizing, intellectually at least, that it is unattainable.
Because he understands what the word "reproduction" means, the audiophile thinks in terms of a relationship to an original sound. This original is, of course, the sound of live music, and the touchstone for its reproduction is accuracy. Unfortunately, though, we don't really compare the reproduction with the real thing—because we can't. Only a recording engineer can saunter back and forth between the real thing (which takes place in a studio or hall) and the reproduction of it (in the control room with its monitor system). We audiophiles must be content to compare the reproduction with what we remember to be the sound of live music. Even the amateur recordist must carry the memory of that original sound home with his tapes in order to evaluate them.
And that memory may not serve us that well. Few of us have learned to listen with enough attention and skill to be able to break live sound down into its components and to observe what each sounds like. Most of us remember only an overall impression—the gestalt of the thing. And many of us must admit, to ourselves at least, that we have not heard live music for years or, worse, never at all. For the vast majority of audiophiles then, the reference standard is not the absolute sound of live music, but an imagined ideal—a mental picture of how we remember its having sounded or how we would like it to sound. At this point, accuracy becomes a dubious criterion because of the vagueness of the original to which we compare the copy. System evaluation becomes a (simple?) matter of "it's good if it sounds good."
The problem with this is that one man's good is another man's distortion. Different people listen to and assign different orders of importance to different aspects of reproduced sound. Thus, while two very picky listeners may agree that a system has good bass, good highs, and a colored middle range, they will disagree as to how good the system is if one happens to be critical of highs and lows while the other is critical of the middle range.
In short, we really don't have any way of reliably assessing the accuracy of reproduced sound. Even a recording engineer cannot be confident of the sound of his own recording, because what he hears in the control room depends on his monitoring equipment, which is no more—and is often less—accurate than a home system. (Many pros do not, in fact, aim for realism at all, but for what they call a "commercial sound"—one that will sell. Thus a recording may not even have the potential for sounding realistic.)
All this does not, however, discourage audiophiles in their search for the Holy Grail of musical accuracy. There are a couple of approaches from which to select. The casual audiophile, who has more interest in music than the ultimate in fi, will usually choose a record label whose releases he favors for their musical values, and will tailor his system to sound best with most of that label's recordings. Discs from other labels may sound good on this system too, but it will be a matter of luck, and bear little relationship to accuracy.
Perfectionist audiophiles, on the other hand, usually aim for maximum accuracy in the playback system itself. The idea here is that, if the system accurately reproduces what is on the recording, the best recordings will yield the most natural sound. (This philosophy has the added benefit of rewarding those record manufacturers who strive hardest for realism.)
This seems like an elegantly simple solution, but there's a flaw. In order to ascertain the accuracy of a disc's reproduction, we must have an original to compare it to. But we can't compare it to the sound that was fed into the master-tape recorder, because that sound was gone forever when the recording session ended. The closest we can get to that original signal is the one that comes from the recorder when the tape is played back. That, after all, is the signal that was used to cut the disc, and if the disc sounds the same as the tape, then we know our record-playing system (the arm, cartridge, and preamp) is accurate. Right? Not necessarily—the record cutting and pressing system was optimized based on a comparison to the original sound, but with probably a completely different phono system than the one you use at home.
Before approving a new release, a record producer is sent a test pressing of it (footnote 1), which he then plays through his reference system and compares with what he hears directly from the master tape. If they don't sound alike, he tells the cutting engineer to make appropriate equalization corrections for the final release cut, or to simply re-cut the disc with the same equalization.
Wouldn't this ensure that his disc sounds like the original tape? Not quite, because it is more than likely that his phono system and preamp have significant colorations, which will make the disc sound different from the way it "actually" sounds. Why, then, should our perfectionist record producer trust his playback system? Because he carefully chose it to make his records sound as much as possible like his tapes!
We've all heard of Catch 22, but in case you're unsure of its meaning, it is about circularity—in reasoning, causality, and Ultimate Truth. Circularity exists when A is a function of B, while B is determined by A. A popular example of circularity is the chicken-or-the-egg question. Then there's the apocryphal "Timbuktu Paradox," which relates the story of the retired sea captain who fires a cannon every day at the precise moment the town hall clock says 12 noon, while the town-hall custodian checks his clock every day by the sound of the 12 o'clock cannon.
What in fact does a record sound like? Think for a moment before answering. It has no sound at all. Hold one up to your ear, and what do you hear? Nothing, of course. To hear what's "on" a recording, you have to reproduce it through a phono system. And what does that phono system really sound like? It sounds like the record with various things added or subtracted. And the music goes 'round and 'round..
There really isn't any way of knowing precisely what is the sound of a record or its player. This is one reason why, in this age of high technology, audio continues to be such a cabalistic field. Where knowledge fails, mysticism moves in.
But just because we cannot make absolute assessments of disc-reproduction accuracy doesn't mean we should abandon the accuracy criterion altogether, any more than we should all stop trying to be good people just because we can't be perfect. There is, in fact, a way we can get reasonably close to the ultimate truth about an analog disc and its player, and that way believe it or not is through the Compact Disc.
The CD has all along been touted as an absolutely accurate recording/playback medium, no doubt to the embarrassment of those manufacturers who so promoted it. Even the mass circulation hi-fi magazines have been reporting that some players sound better than others, and that the best are getting better as time goes on. But another question that has assumed growing importance is just how good the Compact Disc system actually is, because the answer to that question will determine how far the CD can go towards needs of the audiophile who cares about accuracy (footnote 2).
Numbers of audiophile-oriented record manufacturers have been claiming that the CD sound is "virtually indistinguishable from" the sound of the original master tapes. Even allowing for a certain amount of hyperbole (footnote 3), this would seem to indicate that a CD may offer us the most direct path back to the sound of the original master recording. But how much does a CD sound like its master?
To my knowledge, the only investigation of this was done a couple of years ago by England's Hi-Fi News & Record Review. Those listening tests involved direct comparisons between the sound of some Decca CDs and their digital master tapes. The test results were not felt to be entirely conclusive. While there was agreement that the CDs sounded pretty much like the original masters, there was some disagreement as to how important were the minor differences noted.
HFN/RR's experiment is already outdated anyway. Since that time the audio quality of the best CD players has improved dramatically, while many of professional recorders have stayed the same. And the conditions of HFN/RR's tests were not quite the same as an analog disc/tape comparison, because a set of spurious electronics were introduced into the "original" signal: the digital recorder's playback circuitry.
When mastering from analog, the original signal—that is, the signal feeding the cutting system—is already in analog form and can be auditioned directly. But in CD mastering, the original is in digital form, and stays that way up until the time the disc is played in your home. In order to compare the original (digital) with the playback (analog), D/A conversion must occur at the output of the recording deck. And there's the catch. That D/A converter and audio section was not present in the chain that delivered the original signal to the CD. In other words, when we make a CD/master-tape comparison, the "original" sound is being processed by electronics which are different from those used for the CD playback, and the former may not be as good as the latter.
Professional recording equipment is notorious for having less than perfectionist-quality audio circuitry and parts. That's why every recording studio that aims for the best sound customizes its tape decks. Some consumer CD players, such as the Meridian and Mission units, probably produce a better sound from CD digital than do the decks used to master those CDs. So it is more than likely that, if HFN/RR were to repeat those tests today, the CD sound would emerge as the clearcut winner, and would actually be judged better than the "original tape."
Under the circumstances, though, it is likely that such comparisons between the master and the consumer product are more reliable for digital recordings than for analog ones, because there are no mechanical transducers involved. Bad electronics can do some nasty things to digital sound, but they tend to have relatively little effect on the spectral balance of the sound—the balance between bass and treble, and the absolute high-end content. Thus, while we may still quibble over other aspects of CD sound, there is little doubt but that what we hear from a CD is much closer in spectral balance to the master tape than what we hear from an analog reproduction of the same recording.
This is why I adopted CD as my "standard" for judging most aspects of the sound of analog signal sources. Where CDs contrast consistently with what I hear from analog, I assume (on faith, you might say) that the CD sound is closer to the truth in spectral balance and low-frequency quality. If that CD sound is not "good," I do not assume that the better analog sound is "right." Instead, I adjust the other components in my system—the loudspeakers, in particular—until the sound I hear from CD in the listening room is as close as possible to what I remember of live music. This then becomes my standard for evaluating analog sources. The sound I get from analog is of a very high standard, and it has very similar spectral balance to digital sources.
The CD is still not what I consider to be anything like an "absolute" standard, but I do believe it is the closest approach to such an absolute that we're likely to find. It's certainly better than wondering whether the lovely sounds I get from some analog discs are the result of almost-perfect everythings in the chain, or merely a fortuitous mating between gross system colorations all the way from the microphones to the loudspeakers.
http://www.stereophile.com/asweseeit/363/
The typical buyer of a "steeryo" is seeking nothing more than pleasant or exciting sounds, and is easily satisfied because he has no greater expectation of audio than this. The audiophile, however, is aware that reproduced sound can resemble (more or less) real, live sound, and he is driven in a continual search for that ultimate truth ("fidelity to the original") even while realizing, intellectually at least, that it is unattainable.
Because he understands what the word "reproduction" means, the audiophile thinks in terms of a relationship to an original sound. This original is, of course, the sound of live music, and the touchstone for its reproduction is accuracy. Unfortunately, though, we don't really compare the reproduction with the real thing—because we can't. Only a recording engineer can saunter back and forth between the real thing (which takes place in a studio or hall) and the reproduction of it (in the control room with its monitor system). We audiophiles must be content to compare the reproduction with what we remember to be the sound of live music. Even the amateur recordist must carry the memory of that original sound home with his tapes in order to evaluate them.
And that memory may not serve us that well. Few of us have learned to listen with enough attention and skill to be able to break live sound down into its components and to observe what each sounds like. Most of us remember only an overall impression—the gestalt of the thing. And many of us must admit, to ourselves at least, that we have not heard live music for years or, worse, never at all. For the vast majority of audiophiles then, the reference standard is not the absolute sound of live music, but an imagined ideal—a mental picture of how we remember its having sounded or how we would like it to sound. At this point, accuracy becomes a dubious criterion because of the vagueness of the original to which we compare the copy. System evaluation becomes a (simple?) matter of "it's good if it sounds good."
The problem with this is that one man's good is another man's distortion. Different people listen to and assign different orders of importance to different aspects of reproduced sound. Thus, while two very picky listeners may agree that a system has good bass, good highs, and a colored middle range, they will disagree as to how good the system is if one happens to be critical of highs and lows while the other is critical of the middle range.
In short, we really don't have any way of reliably assessing the accuracy of reproduced sound. Even a recording engineer cannot be confident of the sound of his own recording, because what he hears in the control room depends on his monitoring equipment, which is no more—and is often less—accurate than a home system. (Many pros do not, in fact, aim for realism at all, but for what they call a "commercial sound"—one that will sell. Thus a recording may not even have the potential for sounding realistic.)
All this does not, however, discourage audiophiles in their search for the Holy Grail of musical accuracy. There are a couple of approaches from which to select. The casual audiophile, who has more interest in music than the ultimate in fi, will usually choose a record label whose releases he favors for their musical values, and will tailor his system to sound best with most of that label's recordings. Discs from other labels may sound good on this system too, but it will be a matter of luck, and bear little relationship to accuracy.
Perfectionist audiophiles, on the other hand, usually aim for maximum accuracy in the playback system itself. The idea here is that, if the system accurately reproduces what is on the recording, the best recordings will yield the most natural sound. (This philosophy has the added benefit of rewarding those record manufacturers who strive hardest for realism.)
This seems like an elegantly simple solution, but there's a flaw. In order to ascertain the accuracy of a disc's reproduction, we must have an original to compare it to. But we can't compare it to the sound that was fed into the master-tape recorder, because that sound was gone forever when the recording session ended. The closest we can get to that original signal is the one that comes from the recorder when the tape is played back. That, after all, is the signal that was used to cut the disc, and if the disc sounds the same as the tape, then we know our record-playing system (the arm, cartridge, and preamp) is accurate. Right? Not necessarily—the record cutting and pressing system was optimized based on a comparison to the original sound, but with probably a completely different phono system than the one you use at home.
Before approving a new release, a record producer is sent a test pressing of it (footnote 1), which he then plays through his reference system and compares with what he hears directly from the master tape. If they don't sound alike, he tells the cutting engineer to make appropriate equalization corrections for the final release cut, or to simply re-cut the disc with the same equalization.
Wouldn't this ensure that his disc sounds like the original tape? Not quite, because it is more than likely that his phono system and preamp have significant colorations, which will make the disc sound different from the way it "actually" sounds. Why, then, should our perfectionist record producer trust his playback system? Because he carefully chose it to make his records sound as much as possible like his tapes!
We've all heard of Catch 22, but in case you're unsure of its meaning, it is about circularity—in reasoning, causality, and Ultimate Truth. Circularity exists when A is a function of B, while B is determined by A. A popular example of circularity is the chicken-or-the-egg question. Then there's the apocryphal "Timbuktu Paradox," which relates the story of the retired sea captain who fires a cannon every day at the precise moment the town hall clock says 12 noon, while the town-hall custodian checks his clock every day by the sound of the 12 o'clock cannon.
What in fact does a record sound like? Think for a moment before answering. It has no sound at all. Hold one up to your ear, and what do you hear? Nothing, of course. To hear what's "on" a recording, you have to reproduce it through a phono system. And what does that phono system really sound like? It sounds like the record with various things added or subtracted. And the music goes 'round and 'round..
There really isn't any way of knowing precisely what is the sound of a record or its player. This is one reason why, in this age of high technology, audio continues to be such a cabalistic field. Where knowledge fails, mysticism moves in.
But just because we cannot make absolute assessments of disc-reproduction accuracy doesn't mean we should abandon the accuracy criterion altogether, any more than we should all stop trying to be good people just because we can't be perfect. There is, in fact, a way we can get reasonably close to the ultimate truth about an analog disc and its player, and that way believe it or not is through the Compact Disc.
The CD has all along been touted as an absolutely accurate recording/playback medium, no doubt to the embarrassment of those manufacturers who so promoted it. Even the mass circulation hi-fi magazines have been reporting that some players sound better than others, and that the best are getting better as time goes on. But another question that has assumed growing importance is just how good the Compact Disc system actually is, because the answer to that question will determine how far the CD can go towards needs of the audiophile who cares about accuracy (footnote 2).
Numbers of audiophile-oriented record manufacturers have been claiming that the CD sound is "virtually indistinguishable from" the sound of the original master tapes. Even allowing for a certain amount of hyperbole (footnote 3), this would seem to indicate that a CD may offer us the most direct path back to the sound of the original master recording. But how much does a CD sound like its master?
To my knowledge, the only investigation of this was done a couple of years ago by England's Hi-Fi News & Record Review. Those listening tests involved direct comparisons between the sound of some Decca CDs and their digital master tapes. The test results were not felt to be entirely conclusive. While there was agreement that the CDs sounded pretty much like the original masters, there was some disagreement as to how important were the minor differences noted.
HFN/RR's experiment is already outdated anyway. Since that time the audio quality of the best CD players has improved dramatically, while many of professional recorders have stayed the same. And the conditions of HFN/RR's tests were not quite the same as an analog disc/tape comparison, because a set of spurious electronics were introduced into the "original" signal: the digital recorder's playback circuitry.
When mastering from analog, the original signal—that is, the signal feeding the cutting system—is already in analog form and can be auditioned directly. But in CD mastering, the original is in digital form, and stays that way up until the time the disc is played in your home. In order to compare the original (digital) with the playback (analog), D/A conversion must occur at the output of the recording deck. And there's the catch. That D/A converter and audio section was not present in the chain that delivered the original signal to the CD. In other words, when we make a CD/master-tape comparison, the "original" sound is being processed by electronics which are different from those used for the CD playback, and the former may not be as good as the latter.
Professional recording equipment is notorious for having less than perfectionist-quality audio circuitry and parts. That's why every recording studio that aims for the best sound customizes its tape decks. Some consumer CD players, such as the Meridian and Mission units, probably produce a better sound from CD digital than do the decks used to master those CDs. So it is more than likely that, if HFN/RR were to repeat those tests today, the CD sound would emerge as the clearcut winner, and would actually be judged better than the "original tape."
Under the circumstances, though, it is likely that such comparisons between the master and the consumer product are more reliable for digital recordings than for analog ones, because there are no mechanical transducers involved. Bad electronics can do some nasty things to digital sound, but they tend to have relatively little effect on the spectral balance of the sound—the balance between bass and treble, and the absolute high-end content. Thus, while we may still quibble over other aspects of CD sound, there is little doubt but that what we hear from a CD is much closer in spectral balance to the master tape than what we hear from an analog reproduction of the same recording.
This is why I adopted CD as my "standard" for judging most aspects of the sound of analog signal sources. Where CDs contrast consistently with what I hear from analog, I assume (on faith, you might say) that the CD sound is closer to the truth in spectral balance and low-frequency quality. If that CD sound is not "good," I do not assume that the better analog sound is "right." Instead, I adjust the other components in my system—the loudspeakers, in particular—until the sound I hear from CD in the listening room is as close as possible to what I remember of live music. This then becomes my standard for evaluating analog sources. The sound I get from analog is of a very high standard, and it has very similar spectral balance to digital sources.
The CD is still not what I consider to be anything like an "absolute" standard, but I do believe it is the closest approach to such an absolute that we're likely to find. It's certainly better than wondering whether the lovely sounds I get from some analog discs are the result of almost-perfect everythings in the chain, or merely a fortuitous mating between gross system colorations all the way from the microphones to the loudspeakers.
http://www.stereophile.com/asweseeit/363/
Tuesday, May 29, 2007
The Sights and Sounds of Vista
Newsletter #18: Microsoft Remakes Multimedia
When we say Microsoft Vista has some glitz, it's not just marketing; the newest version of Windows sports some revamped video and audio functions designed to promote the digital arts.
We got a hint of the new multimedia even before Vista shipped, as the updated Windows Media Player, and that first look offers a good introduction.
Learn the New Tune
What's new in Windows Media Center?
It has the same basic features as before, but it sports a redesigned menu system, mainly so you can control it from an Xbox 360 over your home network.
Has Windows Media Player changed?
A new interface gives you additional ways to organize and browse your media collection.
For example, you can access your music by an album cover view. Vista's search feature is integrated into Windows Media Player, so you can find media more easily, too. And Windows Media Player includes tie-ins to URGE, a for-pay music service that Microsoft launched with MTV.
Hardware Concerns
Will Vista play HD-DVDs and Blu-ray discs?
Not without third-party software. Though Vista ships with the infrastructure necessary to support HD-DVD--drivers, file system, codecs, and other components--you'll need additional dedicated software to play an HD-DVD video, and the OS has no native support for Blu-ray Disc.
Because of Digital Rights Management for prerecorded high-definition media, will I need to buy a new monitor to play premium high-def content?
You might, regardless of whether you're running Vista or Windows XP. For a PC to send next-generation video content to a display, the display must support HDCP--and while most HDTVs do support this copy-protection technology, many older monitors that support high-def resolutions do not.
http://www.ecoustics.com/pcw/howto/131951
When we say Microsoft Vista has some glitz, it's not just marketing; the newest version of Windows sports some revamped video and audio functions designed to promote the digital arts.
We got a hint of the new multimedia even before Vista shipped, as the updated Windows Media Player, and that first look offers a good introduction.
Learn the New Tune
What's new in Windows Media Center?
It has the same basic features as before, but it sports a redesigned menu system, mainly so you can control it from an Xbox 360 over your home network.
Has Windows Media Player changed?
A new interface gives you additional ways to organize and browse your media collection.
For example, you can access your music by an album cover view. Vista's search feature is integrated into Windows Media Player, so you can find media more easily, too. And Windows Media Player includes tie-ins to URGE, a for-pay music service that Microsoft launched with MTV.
Hardware Concerns
Will Vista play HD-DVDs and Blu-ray discs?
Not without third-party software. Though Vista ships with the infrastructure necessary to support HD-DVD--drivers, file system, codecs, and other components--you'll need additional dedicated software to play an HD-DVD video, and the OS has no native support for Blu-ray Disc.
Because of Digital Rights Management for prerecorded high-definition media, will I need to buy a new monitor to play premium high-def content?
You might, regardless of whether you're running Vista or Windows XP. For a PC to send next-generation video content to a display, the display must support HDCP--and while most HDTVs do support this copy-protection technology, many older monitors that support high-def resolutions do not.
http://www.ecoustics.com/pcw/howto/131951
Do-It-Yourself Surveillance Protects Home or Business
Is that summer downpour flooding your basement? Did Rover get into the garbage again? Is your 50-inch flat-panel TV still in place? Find out from anywhere by using your PC to create an affordable home surveillance system that you can access over the Internet, or even over your cell phone. A professionally installed surveillance system costs at least $2000, but you can set up an uncomplicated USB-connected Webcam such as Logitech's QuickCam Chat for $30, a wireless camera that can be placed almost anywhere for less than $200, or a complete PC-based monitoring system for under $1000.
A basic surveillance system requires three things: a camera; motion-sensing software to activate the camera and to store its video or still images; and software to send the images over the Internet. Adding a wired or wireless network expands your home-surveillance capabilities.
If you're on a tight budget or you don't want to deal with installing remote cameras, an inexpensive Webcam can serve as a bare-bones surveillance device. Many Webcams come with motion-sensing and remote-access software, but paying extra for a full-featured program may be worthwhile, especially if you want to use several Webcams of different makes (for two software recommendations, see " Cameras With Swivel").
The biggest drawback of a Webcam, of course, is that it's tethered by a USB cable to your PC. Powered USB hubs and USB active repeater cables allow you to double or triple USB's 5-meter length limit. Or you can wait for the convenience of wireless USB products, which should arrive soon. In fact, Belkin's CableFree wireless USB hub may be available by the time you read this.
Click to see a full-size image.
IP cameras, on the other hand, can be placed anywhere there's a network connection, making them ideal for homes or offices that already have a wireless network. Since they connect directly to your router rather than through your PC, you don't need to keep the machine on to view the camera's image in a browser. Prices for cameras with such features as night vision, remote-control positioning (pan-and-tilt controls, for instance), and zoom lenses can quickly escalate past $1000, but less expensive wireless cameras like D-Link's DCS-5300G (about $500 online), Linksys's Compact Wireless G Internet Video Camera (about $100 online) and 4XEM's WLPTG Wireless Pan/Tilt IP Network Camera (about $390 online) have many of these extra features.
The pan-and-tilt capability of the 4XEM and D-Link units let me monitor my living room, kitchen, and yard (through a window) with one camera whose view I controlled remotely, rather than having to use two or three stationary cameras. If you have pets, attach a speaker to let them hear your voice from afar.
I installed three different wireless cameras on my wireless network, and though I struggled with the setup, after 5 hours I was monitoring my dog's water bowl, my front door, and my vegetable garden from my cousin's house across town.
Of course, your network camera will only be as useful as the surveillance software that runs it. If the software bundled with your camera is difficult to use, has too limited a set of features, or is impossible to install, you can ditch it and try one of the many third-party alternatives, such as DeskShare's $50 WebCam Monitor or iCode's $79 i-Catcher Sentry. I found both apps much easier to configure and more useful than the programs that came with several of the cameras I tried out.
Before you buy a camera-controller app, make sure its codec works with your cameras. IP cameras typically support either the MJPEG or the MPEG-4 codec, though some newer cameras support both. MPEG-4 cameras produce smaller video files, but at lower resolutions than MJPEG.
Here answers to some common questions about remote surveillance cameras.
How do I power a remote camera? If you want to place a camera somewhere without easy access to an electrical outlet, look for a camera that supports Power over Ethernet (PoE). PoE cameras can draw power from the CAT5 ethernet cable used to transmit data, eliminating the need for a separate power line. Some cameras feature built-in PoE support, while others, such as D-Link's $45 DWL-P200, require a PoE adapter.
What else can I monitor? If you need more than audio or visual confirmation that your home or business is safe and sound, Digi's Watchport Sensors monitor temperature, moisture, and motion. Each sensor connects via USB to a PC and comes with software that sends alerts via e-mail or cell phone. The sensors cost between $130 and $180 online.
Alternatively, Motorola's Homesight Wireless Easy Starter Kit HMEZ2000 monitoring system offers a turnkey home security system with modules for wireless cameras, window and door monitors, and wireless (but not Wi-Fi) temperature and moisture sensors. The starter kit costs about $250. Water, temperature, and window/door sensors cost between $40 and $80 each.
Where do I go for help? Don't waste too much time with a troublesome installation. Call tech support; 4XEM's excellent support line made my setup a breeze, while an hour with a D-Link support tech convinced me to try WebCam Monitor instead of sticking with D-Link's software. My most important lesson: If one quick call to tech support doesn't solve your problem, return your camera for one from a different manufacturer.
Setting up an external link to the Internet can be challenging on any camera. Check out the overview at networkcamerareviews.com and find several useful tips for installing and running an IP camera.
If you print something every day, you probably waste a little something every day as well. TheGreenPrint utility lets you cut down on wasted paper and ink by making it fast and easy to identify and delete unwanted pages, text, or graphics in print jobs. GreenPrint installs as a printer, so if you designate it as your default, it automatically pops up each time you print. At $35 (with a free 14-day trial), the program certainly isn't cheap--but given the price of ink and paper, it can pay for itself pretty quickly.
http://www.ecoustics.com/pcw/howto/131813
A basic surveillance system requires three things: a camera; motion-sensing software to activate the camera and to store its video or still images; and software to send the images over the Internet. Adding a wired or wireless network expands your home-surveillance capabilities.
If you're on a tight budget or you don't want to deal with installing remote cameras, an inexpensive Webcam can serve as a bare-bones surveillance device. Many Webcams come with motion-sensing and remote-access software, but paying extra for a full-featured program may be worthwhile, especially if you want to use several Webcams of different makes (for two software recommendations, see " Cameras With Swivel").
The biggest drawback of a Webcam, of course, is that it's tethered by a USB cable to your PC. Powered USB hubs and USB active repeater cables allow you to double or triple USB's 5-meter length limit. Or you can wait for the convenience of wireless USB products, which should arrive soon. In fact, Belkin's CableFree wireless USB hub may be available by the time you read this.
Click to see a full-size image.
IP cameras, on the other hand, can be placed anywhere there's a network connection, making them ideal for homes or offices that already have a wireless network. Since they connect directly to your router rather than through your PC, you don't need to keep the machine on to view the camera's image in a browser. Prices for cameras with such features as night vision, remote-control positioning (pan-and-tilt controls, for instance), and zoom lenses can quickly escalate past $1000, but less expensive wireless cameras like D-Link's DCS-5300G (about $500 online), Linksys's Compact Wireless G Internet Video Camera (about $100 online) and 4XEM's WLPTG Wireless Pan/Tilt IP Network Camera (about $390 online) have many of these extra features.
The pan-and-tilt capability of the 4XEM and D-Link units let me monitor my living room, kitchen, and yard (through a window) with one camera whose view I controlled remotely, rather than having to use two or three stationary cameras. If you have pets, attach a speaker to let them hear your voice from afar.
I installed three different wireless cameras on my wireless network, and though I struggled with the setup, after 5 hours I was monitoring my dog's water bowl, my front door, and my vegetable garden from my cousin's house across town.
Of course, your network camera will only be as useful as the surveillance software that runs it. If the software bundled with your camera is difficult to use, has too limited a set of features, or is impossible to install, you can ditch it and try one of the many third-party alternatives, such as DeskShare's $50 WebCam Monitor or iCode's $79 i-Catcher Sentry. I found both apps much easier to configure and more useful than the programs that came with several of the cameras I tried out.
Before you buy a camera-controller app, make sure its codec works with your cameras. IP cameras typically support either the MJPEG or the MPEG-4 codec, though some newer cameras support both. MPEG-4 cameras produce smaller video files, but at lower resolutions than MJPEG.
Here answers to some common questions about remote surveillance cameras.
How do I power a remote camera? If you want to place a camera somewhere without easy access to an electrical outlet, look for a camera that supports Power over Ethernet (PoE). PoE cameras can draw power from the CAT5 ethernet cable used to transmit data, eliminating the need for a separate power line. Some cameras feature built-in PoE support, while others, such as D-Link's $45 DWL-P200, require a PoE adapter.
What else can I monitor? If you need more than audio or visual confirmation that your home or business is safe and sound, Digi's Watchport Sensors monitor temperature, moisture, and motion. Each sensor connects via USB to a PC and comes with software that sends alerts via e-mail or cell phone. The sensors cost between $130 and $180 online.
Alternatively, Motorola's Homesight Wireless Easy Starter Kit HMEZ2000 monitoring system offers a turnkey home security system with modules for wireless cameras, window and door monitors, and wireless (but not Wi-Fi) temperature and moisture sensors. The starter kit costs about $250. Water, temperature, and window/door sensors cost between $40 and $80 each.
Where do I go for help? Don't waste too much time with a troublesome installation. Call tech support; 4XEM's excellent support line made my setup a breeze, while an hour with a D-Link support tech convinced me to try WebCam Monitor instead of sticking with D-Link's software. My most important lesson: If one quick call to tech support doesn't solve your problem, return your camera for one from a different manufacturer.
Setting up an external link to the Internet can be challenging on any camera. Check out the overview at networkcamerareviews.com and find several useful tips for installing and running an IP camera.
If you print something every day, you probably waste a little something every day as well. TheGreenPrint utility lets you cut down on wasted paper and ink by making it fast and easy to identify and delete unwanted pages, text, or graphics in print jobs. GreenPrint installs as a printer, so if you designate it as your default, it automatically pops up each time you print. At $35 (with a free 14-day trial), the program certainly isn't cheap--but given the price of ink and paper, it can pay for itself pretty quickly.
http://www.ecoustics.com/pcw/howto/131813
Ten Things You Need to Know About 1080p
New models of consumer electronics products almost change with the seasons: you've finally understood why you need a High Definition Television (HDTV) when along comes yet another electronic upgrade. As exciting as these developments are, they may also provoke vague feelings of discontent. This can occur if some know-it-all points out that your HD display is only 720p. When this happened to me recently, I countered with the fact that I was viewing HDTV while this person was still in nursery school. (Japan developed an analog version of HDTV in the 1980s, which I saw on press trips to Japan and later viewed in Canada when TV broadcasters there considered adopting the Japanese HDTV system for the future needs of Canadian TV broadcasting. It was ultimately rejected.)
hdtv
As many readers are aware, the "1080p" tide has been rising for at least a year and this spring it seems to have reached a new high-water mark, in part stimulated by the market appearance of new high-definition DVD players: HD-DVD and Blu-ray, recorded and studio mastered in 1080p. These two formats are not compatible (except for LG's HD-DVD/Blu-ray combo player, and a new combo unit due from Samsung), however they will play your existing DVDs.
Resisting the marketing juggernaut is never easy (we really know how to consume in the 21st century) so in the spirit of both welcoming and explaining 1080p, here are some guidelines to help you navigate the claims and counter claims:
1. What is it? "1080p" stands for 1080 progressive. It means that a video display or video source has the capability to display a high-definition video image made up of 1080 horizontal "lines" progressively scanned from the top to the bottom of the screen. Your old analog CRT set yielded about 330 lines. A standard DVD player delivers 480 lines. In techie terms, a 1080p high-definition set will display an image comprised of 1920 x 1080 pixels, or approximately 2 million pixels (a pixel is a picture element) versus a 720p image, which consists of 1280 x 720 pixels, or about 921,600 pixels. Other things being equal, the more pixels there are in an image, the greater the potential detail and clarity.
"1080p" is a refinement of HD video technology that has evolved from earlier HD displays known as 720p or 1080i (i for interlaced). The latter (720p or 1080i) are the existing standards for HD images broadcast over the air or by cable or satellite. Broadcast 1080p images are not available -- yet. But they may be some years down the road.
2. If you own or buy a new 1080p set, it will convert or upscale incoming 720p or 1080i images to 1080p. The upscaled images may look smoother and more nuanced, clearer if you will, than those viewed on a 720p set.
3. If you already own an HD set that is several years old, it will likely be a 720p model (rarely 1080i unless it's a CRT HD set), so there is no point in getting video sources that deliver a 1080p image because your video device can't display the extra pixels, unless of course you decide to replace your 720p or 1080i HDTV with a 1080p HDTV.
4. If you are deliberating about buying a new 1080p large screen display, then it will let you do two things: either sit closer to the screen than you otherwise could if you had a 720p display, or, if you decide to go for a 1080p front projector, then you could project a considerably bigger screen image that would look as clear and sharp as a 720p image viewed from twice as far back.
For very large TV displays -- 65 inches diagonal, say, or projected images of 96 or 108 inches, you would see more detail from viewing distances of 5, 8, or 9 feet, respectively. Note that 9 feet is currently the average viewing distance for TV in most homes. On the other hand, because a 1080p set has almost twice as many pixels as a 720p display, subtleties and gradations of color and texture should be better, and visible.
5. Some new AV receivers and DVD players have built-in video up-conversion and scaling to 1080p. The upconversion to 1080p done in an AV receiver is only a convenience, and may not be executed as well as the conversion performed internally in your 1080p video display or projector.
6. Note that any 1080p display or 1080p projector will, on its own, upconvert any incoming standard or high-definition video source connected to it to 1080p. You do not need to purchase an outboard scaler in an AV receiver to perform that function. Your 1080p set will do that automatically because it must in order to display the image and fill all the pixels. (Techies call the latter the set’s "native resolution" -- 1080p.)
7. You should also note that upconversion (scaling) to 1080p of standard definition (SD) video sources like regular DVDs or standard TV broadcasts will not make them look like a true HD image (720p or 1080i). They may appear smoother to the eye, but detail cannot be added by up-conversion.
8. The only sources currently available for true 1080p images are HD-DVD and Blu-ray discs, and those must be delivered from an HD-DVD or Blu-ray disc player via HDMI cables. HDMI connections carry video images as well as standard images -- and 1080p -- in digital form, whereas component video cables are analog and carry 720p or 1080i HD images. While component video cables are technically able to pass 1080p images, Hollywood studios do not permit 1080p discs to be made without the anti-piracy digital handshake code that must be passed via HDMI cables. HD-DVD or Blu-ray players will only output 1080p signals over HDMI connections.
9. Finally, if you use a 50-inch to 60-inch diagonal HD display, and plan on sitting farther than 10 feet away from it, the 1080p display may not look any clearer than a 720p display would at that distance, however you may perceive a slightly smoother and more satisfying picture from the 1080p set. Still, we are talking subtleties here. Only if you sit 5 feet or so from a 60-inch 1080p screen will the increased clarity of 1080p be immediately apparent.
10. If you are about to purchase an HD set, then getting a 1080p display will "future-proof" your system because it will display the maximum picture resolution from HD-DVD or Blu-ray discs no matter which format "wins", and it will be capable of displaying the highest clarity possible for almost any new video delivery system coming down the pipe. Of course, as we discussed earlier, there is always something else on the horizon, including the huge palette of colors obtainable with Deep Color, which new 1080p sets will be able to access through the latest version of HDMI 1.3 connections this fall.
http://forum.ecoustics.com/bbs/messages/34579/356979.html
hdtv
As many readers are aware, the "1080p" tide has been rising for at least a year and this spring it seems to have reached a new high-water mark, in part stimulated by the market appearance of new high-definition DVD players: HD-DVD and Blu-ray, recorded and studio mastered in 1080p. These two formats are not compatible (except for LG's HD-DVD/Blu-ray combo player, and a new combo unit due from Samsung), however they will play your existing DVDs.
Resisting the marketing juggernaut is never easy (we really know how to consume in the 21st century) so in the spirit of both welcoming and explaining 1080p, here are some guidelines to help you navigate the claims and counter claims:
1. What is it? "1080p" stands for 1080 progressive. It means that a video display or video source has the capability to display a high-definition video image made up of 1080 horizontal "lines" progressively scanned from the top to the bottom of the screen. Your old analog CRT set yielded about 330 lines. A standard DVD player delivers 480 lines. In techie terms, a 1080p high-definition set will display an image comprised of 1920 x 1080 pixels, or approximately 2 million pixels (a pixel is a picture element) versus a 720p image, which consists of 1280 x 720 pixels, or about 921,600 pixels. Other things being equal, the more pixels there are in an image, the greater the potential detail and clarity.
"1080p" is a refinement of HD video technology that has evolved from earlier HD displays known as 720p or 1080i (i for interlaced). The latter (720p or 1080i) are the existing standards for HD images broadcast over the air or by cable or satellite. Broadcast 1080p images are not available -- yet. But they may be some years down the road.
2. If you own or buy a new 1080p set, it will convert or upscale incoming 720p or 1080i images to 1080p. The upscaled images may look smoother and more nuanced, clearer if you will, than those viewed on a 720p set.
3. If you already own an HD set that is several years old, it will likely be a 720p model (rarely 1080i unless it's a CRT HD set), so there is no point in getting video sources that deliver a 1080p image because your video device can't display the extra pixels, unless of course you decide to replace your 720p or 1080i HDTV with a 1080p HDTV.
4. If you are deliberating about buying a new 1080p large screen display, then it will let you do two things: either sit closer to the screen than you otherwise could if you had a 720p display, or, if you decide to go for a 1080p front projector, then you could project a considerably bigger screen image that would look as clear and sharp as a 720p image viewed from twice as far back.
For very large TV displays -- 65 inches diagonal, say, or projected images of 96 or 108 inches, you would see more detail from viewing distances of 5, 8, or 9 feet, respectively. Note that 9 feet is currently the average viewing distance for TV in most homes. On the other hand, because a 1080p set has almost twice as many pixels as a 720p display, subtleties and gradations of color and texture should be better, and visible.
5. Some new AV receivers and DVD players have built-in video up-conversion and scaling to 1080p. The upconversion to 1080p done in an AV receiver is only a convenience, and may not be executed as well as the conversion performed internally in your 1080p video display or projector.
6. Note that any 1080p display or 1080p projector will, on its own, upconvert any incoming standard or high-definition video source connected to it to 1080p. You do not need to purchase an outboard scaler in an AV receiver to perform that function. Your 1080p set will do that automatically because it must in order to display the image and fill all the pixels. (Techies call the latter the set’s "native resolution" -- 1080p.)
7. You should also note that upconversion (scaling) to 1080p of standard definition (SD) video sources like regular DVDs or standard TV broadcasts will not make them look like a true HD image (720p or 1080i). They may appear smoother to the eye, but detail cannot be added by up-conversion.
8. The only sources currently available for true 1080p images are HD-DVD and Blu-ray discs, and those must be delivered from an HD-DVD or Blu-ray disc player via HDMI cables. HDMI connections carry video images as well as standard images -- and 1080p -- in digital form, whereas component video cables are analog and carry 720p or 1080i HD images. While component video cables are technically able to pass 1080p images, Hollywood studios do not permit 1080p discs to be made without the anti-piracy digital handshake code that must be passed via HDMI cables. HD-DVD or Blu-ray players will only output 1080p signals over HDMI connections.
9. Finally, if you use a 50-inch to 60-inch diagonal HD display, and plan on sitting farther than 10 feet away from it, the 1080p display may not look any clearer than a 720p display would at that distance, however you may perceive a slightly smoother and more satisfying picture from the 1080p set. Still, we are talking subtleties here. Only if you sit 5 feet or so from a 60-inch 1080p screen will the increased clarity of 1080p be immediately apparent.
10. If you are about to purchase an HD set, then getting a 1080p display will "future-proof" your system because it will display the maximum picture resolution from HD-DVD or Blu-ray discs no matter which format "wins", and it will be capable of displaying the highest clarity possible for almost any new video delivery system coming down the pipe. Of course, as we discussed earlier, there is always something else on the horizon, including the huge palette of colors obtainable with Deep Color, which new 1080p sets will be able to access through the latest version of HDMI 1.3 connections this fall.
http://forum.ecoustics.com/bbs/messages/34579/356979.html
Stunning Photos With High Dynamic Range, Part 2
Use specialized software to combine images for a great effect.
If you've ever photographed an idyllic landscape and ended up with a washed-out sky and dark, underexposed blobs instead of shadows, you'll understand why photographers are falling in love with High Dynamic Range photography. HDR allows you to capture far more color, brightness, and contrast information in photos than has been possible.
Last week we talked about how to capture the series of photos that would become part of our HDR masterpiece.
Combining the Images
Shooting the series was half the battle; now it's time to combine the photos into a single image that takes all the best parts of each.
You've got a wide choice of programs to create HDR photos. Adobe Photoshop CS2, for example, has an HDR feature. So does Ulead PhotoImpact. There are also some stand-alone HDR utilities out there, like Photogenics HDR and Photomatix Pro.
I downloaded the free trial version of Photomatix Pro. There's no time limit on how long you can use the trial version, but it inscribes a watermark across each of your photos unless you pay $99 for the license.
Using Photomatix Pro
To use the program, drag your set of bracketed photos into the program window and wait for them to display. If you haven't made any HDR photos of your own yet, here are some sample source images you can use (I took these photos on a tripod in front of my house near dusk):
Choose HDR, Generate from the menu and click OK when the program asks if you want to use the open images.
In the next dialog box, select the check box to align the source images--this lines up your photos in case you were handholding the camera or the tripod moved a bit between shots--and choose the default "standard tone curve." Click OK.
After some processing time, you'll get a result. It probably won't look very good, but don't worry: The composite image holds more contrast information than a typical computer display is capable of showing. The final step is to optimize the image for the screen. Choose HDR, Tone Mapping from the menu.
On this final screen, you can tweak many aspects of the photo, such as the white and black levels, the color saturation, and contrast levels. Feel free to experiment with the settings.
Click for full image.
You'll probably find that often you can just click OK to accept the defaults; the results will look impressive without much tweaking. I used a series of five photos for my HDR image, which appears on the right.
HDR isn't perfect. Because it relies on a series of photos, it's not appropriate for action photography--or, in fact, photos in which pretty much anything moves at all. It requires meticulous setup, a tripod, enough patience to configure a series of bracketed images--and, of course, the software to glue it all together at the end. But if you can deal with those shortcomings, you can make some photos that are nothing short of stunning.
Hot Pic of the Week
Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique. Every month, the best of the weekly winners gets a prize valued at between $15 and $50.
Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.
Click for full image.
This Week's Hot Pic: "Summer Snack," by Patrick Marcigliano, Cumming, Georgia
Patrick says: "I took this shot of my daughter at a beach house after she had just come in from the beach to eat some lunch. She was hopping up and down at the table's edge, playing hide and seek with me. I just happened to catch her when she paused for just a second to see what I would do."
http://www.ecoustics.com/pcw/howto/131612
If you've ever photographed an idyllic landscape and ended up with a washed-out sky and dark, underexposed blobs instead of shadows, you'll understand why photographers are falling in love with High Dynamic Range photography. HDR allows you to capture far more color, brightness, and contrast information in photos than has been possible.
Last week we talked about how to capture the series of photos that would become part of our HDR masterpiece.
Combining the Images
Shooting the series was half the battle; now it's time to combine the photos into a single image that takes all the best parts of each.
You've got a wide choice of programs to create HDR photos. Adobe Photoshop CS2, for example, has an HDR feature. So does Ulead PhotoImpact. There are also some stand-alone HDR utilities out there, like Photogenics HDR and Photomatix Pro.
I downloaded the free trial version of Photomatix Pro. There's no time limit on how long you can use the trial version, but it inscribes a watermark across each of your photos unless you pay $99 for the license.
Using Photomatix Pro
To use the program, drag your set of bracketed photos into the program window and wait for them to display. If you haven't made any HDR photos of your own yet, here are some sample source images you can use (I took these photos on a tripod in front of my house near dusk):
Choose HDR, Generate from the menu and click OK when the program asks if you want to use the open images.
In the next dialog box, select the check box to align the source images--this lines up your photos in case you were handholding the camera or the tripod moved a bit between shots--and choose the default "standard tone curve." Click OK.
After some processing time, you'll get a result. It probably won't look very good, but don't worry: The composite image holds more contrast information than a typical computer display is capable of showing. The final step is to optimize the image for the screen. Choose HDR, Tone Mapping from the menu.
On this final screen, you can tweak many aspects of the photo, such as the white and black levels, the color saturation, and contrast levels. Feel free to experiment with the settings.
Click for full image.
You'll probably find that often you can just click OK to accept the defaults; the results will look impressive without much tweaking. I used a series of five photos for my HDR image, which appears on the right.
HDR isn't perfect. Because it relies on a series of photos, it's not appropriate for action photography--or, in fact, photos in which pretty much anything moves at all. It requires meticulous setup, a tripod, enough patience to configure a series of bracketed images--and, of course, the software to glue it all together at the end. But if you can deal with those shortcomings, you can make some photos that are nothing short of stunning.
Hot Pic of the Week
Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique. Every month, the best of the weekly winners gets a prize valued at between $15 and $50.
Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.
Click for full image.
This Week's Hot Pic: "Summer Snack," by Patrick Marcigliano, Cumming, Georgia
Patrick says: "I took this shot of my daughter at a beach house after she had just come in from the beach to eat some lunch. She was hopping up and down at the table's edge, playing hide and seek with me. I just happened to catch her when she paused for just a second to see what I would do."
http://www.ecoustics.com/pcw/howto/131612
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