Photo

I work a mere four blocks away from the Moscone Center, where the annual MacWorld SF trade show is held, so naturally I just drift there during my lunch break, possibly extended… Here is a list of strange and wonderful things I saw during the show, and that might have been overlooked by the more mainstream sites:

iLugger

The iLugger is a carrying case for the iMac G5 (it fits both the 17″ and 20″ models). Most laptops are always connected to the mains and seldom used as real mobile devices, and an iMac G5 will give significantly better performance at 2/3 the price of a PowerBook. Interestingly, the company making it is a blimp manufacturer, clearly a case of someone scratching their own itch.

Epson RD-1

Not a new product, but I got to handle an Epson R-D1, a limited edition Leica M compatible rangefinder digital camera (the only one of its kind) based on a Voigtländer-Cosina Bessa R2 body. I shot a few samples with a 50mm Summicron and Noctilux, and the resulting pictures are remarkable clear and sharp. Noise levels at ISO 800 are significantly better than my Canon EOS 10D, no small feat, and given a rangefinder’s 2-3 stop advantage over a SLR, this looks like an ideal available-light camera.

The Bessa R2 has a relatively short rangefinder base length, which reduces its focusing accuracy compared to a Leica. The hardest lens to focus is the Noctilux-M 50mm f/1.0 (yes, you read that right, the fastest production lens in the world), due to its very shallow depth of field at low aperture, as shown in the picture to the left. I took it with a Noctilux (ISO 200, f/1.0, 1/125) at close to its minimum distance of 1 meter, and focusing accuracy seems adequate… Click on the image for the full-size JPEG with EXIF metadata (not including the manually set aperture and focus, of course). For comparison purposes, here is the corresponding JPEG I shot yesterday (ISO 800, Summicron-M 50mm f/2, 1/30, aperture unrecorded, probably f/4).

The gentleman portrayed is an Epson representative who was apparently given the charge of watching over this $3000 camera (apparently his only task). The sight of me pawing over it might explain his expression…

I won’t duplicate Luminous Landscape’s review, and didn’t have that much time to play with the RD-1 in any case. Build quality is good, as good as the 10D at least. It does not have the satisfying heft of my Leica MP, nor its superlative 0.85x viewfinder, but then again what does? Some retro touches like the dials are an affectation, as well as the manually cocked shutter. The shutter cocking lever does not have to advance film, and its short travel feels somewhat odd.

X-Rite Pulse ColorElite

X-Rite, a maker of color calibration hardware, was demonstrating its Pulse ColorElite bundle, resulting from its acquisition of the color management software vendor Monaco Systems. This package allows you to calibrate with precision the color characteristics of a monitor, scanner, digital camera and printer, for consistent, professional-grade color management. It goes much beyond simple and now relatively inexpensive monitor calibration colorimeters, by also using a spectrophotometer (an instrument that measures light across the visible spectrum, wavelength by wavelength), and the price is correspondingly higher. The market-leading product is the GretagMacbeth Eye-One Photo. X-Rite has clearly replicated the Eye-One package, but at a slightly lower price, and with some nice touches that significantly improve usability. The Eye-One spectrophotometer (which is used both for calibrating monitors and prints, a GretagMacbeth patented technology) is reportedly more accurate, however (3nm vs. 20nm). The Pulse bundle retails for $1300, the Eye-One for $1400.

FrogPad

The FrogPad is a small one-handed Bluetooth keyboard designed to be used with PDAs or smartphones, but it can also be used with a Mac or PC as it follows the standard Bluetooth Human Interface Device (HID) profile. You can hold it in one hand and type with the other. I don’t know how long it takes to get used to it, but at any rate they are offering $50 off the regular price of $179 if you use the code Apple50. They also has a mockup of a folding version in cloth, for use in wearable computing.

Interwrite Bluetooth tablet

CalComp used to make high-end tablets and digitizers for architects, engineers and artists. The tablet market is pretty much monopolized by Wacom, nowadays, but CalComp is still around (after being bought out by GTCO). They were demonstrating a Bluetooth tablet for use by teachers in a classroom setting (although I am not sure how many cash-strapped school districts can afford the $800 device).

JetPhoto

There was a cluster of small Chinese companies exhibiting. One of the more interesting was Atomix, a company that makes JetPhoto, a digital photo asset management database, similar to Canto Cumulus or Extensis Portfolio. Apparently, their forte is the integration of GPS metadata and the image database, you can do geographical selections on a map to find photos. It also had many export functions with a comprehensive database of cell phones and PDAs to export photos to. Unfortunately, the current version does not support sophisticated hierarchical, set-oriented categories, the one feature in IMatch I find absolutely vital.

The program looked impressively polished for a first version, and is available free to download for now. This is yet another illustration of how the Chinese are rapidly advancing up the value chain, and American firms could be in for a nasty surprise if they maintain the complacent belief high-end jobs are their birthright and only unqualified manufacturing jobs or menial IT tasks are vulnerable to Chinese (or Indian) competition.

Fujitsu ScanSnap

One of the few things I still use my Windows game console PC for is to drive my Canon DR-2080C document scanner. This small machine, the size of a compact fax machine, can scan to PDF 20 pages per minute (and it can scan both sides simultaneously). It is intended for corporate document management, but is also very useful to tame the paper tiger by batch-converting invoices, bills and so onto purely electronic form, in a way that is not practical using a flatbed scanner.

It seems Fujitsu is bringing that functionality to the Mac with the similarly specified ScanSnap fi-5110EOX. The scanner is driven with a bundled version of Adobe Acrobat 6.0. I can well see this becoming popular in small businesses run on Macs, although the Fujitsu reps on the stand implied they were here to gather potential customer feedback to make a stronger case for enhanced Mac support with their management and accelerate the release of Mac drivers for it.

Ovolab Phlink

My office PBX is actually a PC-based CTI unit made by Altigen, and voice mails left to me are automatically forwarded to me as WAV attachments in an email. That has major usability benefits – I can set email rules to drop voice mails when the attachment is too small (usually someone who hanged up on the voice mail prompt), or fast forward and rewind during message replay. This feature is addictive – voice mail still sucks compared to email (disk hogging, not searchable or quickly scannable), but being liberated from excruciatingly slow voice-driven user interfaces, replete with unnecessarily deliberate and verbose prompting, makes it somewhat bearable.

I did not have this kind of functionality at home, however. It is possible VoIP devices will offer it at some point, but that does not seem to be the case in low-end home VoIP for now. I tried experimenting with the open-source Asterisk PBX, but did not have the time to pursue this, and in any case I’d rather not have to install a dedicated Linux machine at home just for this purpose (my home network runs on Solaris/x86, thank you very much).

Fortunately, Ovolab, an Italian company based near Milan, has introduced Phlink, just what I was searching for, and I actually bought one on the spot. It is a small USB telephony attachment that plugs into a phone line and turns your Mac into a sophisticated CTI voice-mail system. It is fully scriptable using AppleScript and supports Caller ID. I have yet to use it extensively (the hardest part, interestingly, is bringing a phone cord close enough to my Mac).

The photography world learned yesterday the sad but not entirely unexpected news of Henri Cartier-Bresson’s demise. Cartier-Bresson was 96 years old, and had prepared his legacy by setting up a retrospective and foundation in Paris. The catalog of the retrospective is one of the finest coffee-table books you can get, by the way. Cartier-Bresson is best known for his theory of the “decisive moment”. Although some wags would say the decisive moment was really when he reviewed his contact sheets, Cartier-Bresson clearly perfected a technique of anticipating the event and being ready to capture it on film, helped in this by his Leica rangefinder cameras.

Cartier-Bresson was known for his caustic wit and his often provocative statements. In an interview to Le Monde, he derided the “academic clichés of Weston” (les poncifs académiques de Weston), referring no doubt to Edward Weston’s still life studies of peppers. Someone using lightweight equipment like Cartier-Bresson has the luxury of spontaneity large-format photographers like Weston did not. Indeed, Brett Weston, Edward Weston’s second son, quipped that “Anything more than 500 yards from the car just isn’t photogenic” when working with a 8×10 view camera.

You don’t have to carry a behemoth camera to realize the virtues of forward planning. When doing landscape photography, it is helpful to know ahead of time what kind of lens or camera to pack, and the position of the sun. There are many ephemeris tables online to find the latter, but the easiest way to select a lens is to use a map. You could use a protractor to measure angles, but they are relatively small and fiddly to use. As I often shoot with a Fuji G617 panoramic camera and a Hasselblad system, I made a series of translucent templates to help with this – all I need to do is superimpose them on the map (such as a 1:24,000 topographic map produced by a National Geographic map machine).

I wrote a quick program in Python and PostScript to produce templates in PDF format for various film formats and lens focal lengths, ready to print on a laser printer (I used Four Corners Paper IFR Vellum). I hope this will be useful. As an example, here is the template I use with my Fuji G617.

Layout

A4 US Letter Portrait Landscape

Film format 35mm 1.6x DSLR 1.3x DSLR 65mm (XPan) 6x6 6x7 6x9 6x12 6x17 4x5 5x7 8x10    Focal length mm (separate multiple lengths with spaces)

Harking back to Kodachrome

My father took most of my childhood photos (like these) on Kodachrome slide film. Kodachrome was the only color game in town for a long time, but was eventually superseded in the marketplace by C41 color print films and finer grained E6 slide film.

Kodachrome has a distinctive sharpness (acutance, not resolution), and excellent durability when stored in the dark. Many photographers still shoot Kodachrome for its special “look”, even though processing options are diminishing and Kodak jacked up the price. Kodak recently announced it is closing its Fair Lawn, NJ processing lab, the last Kodak-owned plant in the US for Kodachrome, and there are now only three labs left worldwide that can run the complicated process (Dwayne’s in Kansas, Kodak in Lausanne, Switzerland, and a lab in Japan). Kodachrome was actually discontinued for a while, and brought back after strident protests, but the writing is on the wall.

Projectors and light tables

Every now and then, we would dust off the slide projector and have a slide show. I even remember building a surprisingly effective slide projector when I was 9 using Legos, a flashlight and a jar of peanut butter filled with water as the lens. Slide projectors are hard to find, a pain to setup and most people groan instinctively when one comes up, associated as they are with dreary slide show of other people’s vacation pictures. The LCD computer monitor is the successor to the projector, and many people no longer have prints made at all, perhaps because they subconsciously realize that the 500:1 contrast ratio of a LCD monitor yields significantly livelier images than prints can achieve.

A light table is just what the name implies – a piece of frosted plastic illuminated by daylight-balanced fluorescent tubes. Basic models like my Porta-trace shown above are inexpensive. Loupes, on the other hand, are a different story.

Loupe basics

Loupes (French for “magnifying glass”) are high-quality magnifiers, originally used to help focus images on a ground glass, and later to view slides or negatives on a light table. You can find them in all shapes and sizes, at prices from $15 for a cheap plastic model, all the way to over $300 for a Zeiss loupe for viewing 6×6 medium format slides. Slides viewed on a light table with a high-quality loupe are a treat for the eyes, because of the high contrast (1000:1) that you cannot get with prints (more like 100:1).

There are two ways you can use a loupe: use a high-power (10x or higher) to check slides or negatives for critical focus), or a medium-power loupe to evaluate an entire frame (usually 5x-6x for 35mm, 3x-3.5x for medium format). Viewing an entire frame is more challenging than just checking for focus in the center, because the loupe must provide excellent optical quality across the entire field of view. There are variable magnification (zoom) loupes available, but their optical quality is far below that of fixed magnification loupes, and they should be avoided for critical examination of slides or negatives.

I have accumulated quite a few loupes over time. The most famous brand in loupes is Schneider-Kreuznach, a German company noted for its enlarger, medium format and large format lenses. Many other brands make high-quality loupes, including Rodenstock, Pentax, Nikon, Canon, NPC, Leica and Zeiss. I do not live in New York, and have thus not had the opportunity to compare them side by side at a place like B&H Photo, so I pretty much had to take a leap of faith based on recommendations on the Internet at sites like Photo.net.

• Peak 10x Plalupe
• Contax Carl Zeiss Triotar T* 5x (larger photo)
• Edmund Optics 50x direct view measuring microscope
• Calumet-branded Rodenstock 3x Aspherical loupe for 6×6
• Calumet-branded Rodenstock 4x Aspherical loupe for 35mm
• Edmund Optics 10x Hastings Triplet
• Schneider 10x magnifier

Peak

The Peak was my first loupe. Dirt cheap, and reasonably good for the price, but that’s pretty much all it has going for it (more on that below).

Zeiss

I was put off by reports on the plastic construction of the new line of Schneider loupes, and opted for a Zeiss loupe instead, based on the reputation of Zeiss lenses (my first camera was a Zeiss, and I also have a Zeiss lens on my Hasselblad).

The Zeiss Triotar 5x loupe (the box does not mention Contax, but as it is made in Japan, it is presumably made in the same factory) comes in a cardboard box that can be turned into a protective case by cutting off the tabs on both ends. It does not include a carrying pouch or protective box, which is regrettable, specially for a product as expensive ($160), but apparently most high-end loupe manufacturers do not bother to include one. It does not include a neck strap either, which could be more of an issue for some. How can you look like a glamorous New York art director without a loupe around your neck? More seriously, the strap is particularly useful if you are going to use the loupe for focusing medium or large format cameras against a ground screen.

The loupe is shipped with two acrylic bases that screw into the loupe’s base. One is frosted, and is used as a magnifier to view prints or other objects, with ambient light filtering through the base to illuminate the object. The black base is used to shield out extraneous light when concentrating on a slide or negative on a light table or a ground glass. Some loupes have a design with a clear base and a removable metal light shield. Which design you prefer is mostly a matter of personal taste. The loupe has a pleasant heft to it, and impeccable build quality. The main body of the loupe itself is solidly built of black anodized metal, with a knurled rubber focusing ring.

The optical quality is what you would expect form Zeiss. Crystal clear, sharp across the field of view, and no trace of chromatic aberration in the corners. You can easily view an entire 35mm frame and then some, although I suspect eyeglass wearers might find the eye relief a little bit short.

Edmunds pocket microscope

The Edmunds direct view microscope is a versatile instrument, available in many magnifications, with or without an acrylic base (highly recommended) and with or without a measurement reticle (metric or imperial). Due to the high magnification, the image has a very narrow field of view (only 3mm), and is quite dim. Unlike the others, the image is reversed, which requires some adaptation time. The level of detail you can observe on slides taken with a good film like Fuji Provia 100F, using a good lens and a tripod, is absolutely stunning. This is a rather specialized instrument, but well worth having in your toolkit.

Rodenstock

The Rodenstock 3x 6×6 aspheric loupe has a list price of $350 and usually retails for $250. Calumet Photo sells the exact same loupe under their own brand for a mere $149 (I actually got mine for $109 during a promotion), which is not that much more than a cheap (in more ways than price) Russian-made Horizon.

There are naturally fewer loupes available to view medium format slides or negatives than for 35mm. Schneider, Mamiya/Cabin, Contax/Zeiss and Rodenstock make high-grade loupes for this demanding market. If you have a “chimney” viewfinder on your MF camera, you can actually use that as a loupe.

Rodenstock is famous for its large-format and enlarging lenses, and this loupe is very highly rated. The construction is plastic, but still well-balanced and not too top-heavy. It does not carry the feel of opulence that the Zeiss has, or even the very nicely designed Mamiya/Cabin loupes (more on that below), but is still clearly a professional instrument. It has a two-element aspherical design for sharpness across the entire field of view, and coated optics. It comes with a red neck cord, and the base has a removable plastic skirt that slides in place and can be reversed between its clear and dark positions. The eyepiece has a rubber eyecup and a knurled rubber grip for the focusing ring.

I compared it side by side at Calumet San Francisco with the Cabin 3.5x loupe for 6×4.5 or 6×6. The Cabin had a solid metal constuction (somewhat top-heavy), but its screw-in skirts are less convenient than the slide-in one used in the Rodenstock, and the image circle is too tight for my Hasselblad 6×6 slides. I think that loupe was really designed for 645 format and opportunistically marketed for 6×6, when the 6×7 loupe would actually be more appropriate for that usage. The optical quality is very similar and both are excellent loupes. I did not try the Mamiya/Cabin 6×7, unfortunately, as it was not available in the store, but in any case the Rodenstock was a steal.

The optics are excellent, as could be expected, with crisp resolution all the way into the corners and no trace of chromatic aberrations. There is a smidgen of pincushion distortion, however, but not enough to be objectionable (I took the slightly convex curved square skirt out to make sure this was not just an optical illusion).

One thing to watch out for: even though the optics are coated, they are very wide and you have to be careful to keep your eye flush with the eyecup to obscure any overhead light sources like lightbulbs or fluorescent panels and avoid seeing their reflections in the loupe’s glass.

The most comprehensive resource for medium format loupes on the Web is Robert Monaghan’s page on the subject.

Edmunds Hastings triplet

This isn’t really a competitor to the other loupes, as it has a very narrow field of view of only 10mm in diameter. It is also tiny, and I carry mine in my gadget bag. It has a folding jeweler’s loupe design with a folding metallic shield to protect it. Optical quality is of the highest order.

Schneider 10x

Despite its plastic construction, this loupe exudes quality. Unfortunately, the strap is really flimsy – the rubber cord is merely glued into the metal clip, and will easily pull out. I glued mine back, and crimped it with needle-nose pliers for good measure, but I don’t know how robust this arrangement will be.

The optics are excellent, without any trace of chromatic aberration. The usable field of view is surprisingly wide for a loupe with this magnifying power, although your eye has to be perfectly positioned to see it. I estimate the FOV diameter at 20mm, as you can almost see the full height of a 35mm mounted slide. I have an Edmund Optics magnifier resolution chart (it came with the Hastings triplet), and the Schneider outresolves it across the field of view . This means the Schneider exceeds 114 line pairs per millimeter across the frame, quite remarkable performance.

The importance of a good loupe

For a real-world test, I took my 6×17 format Velvia 100F slides of the Golden Gate Bridge, and looked at the suspension cables. The picture to the left shows the details I was looking at (but the fuzzy 1200dpi scan on an Epson 3170 does not remotely do justice to the original). Each bundle of 4 cables (4 line pairs) takes 0.04mm on the slide (I used the 50x Edmunds inspection microscope to measure this), hence you need 100lp/mm to resolve it. The Schneider 10x, Edmunds 10x and Zeiss 5x loupes all resolve the four cables clearly. My old el cheapo Peak 10x loupe did not, nor the Epson scanner, which led me until recently to believe my slides were slightly blurry because I had forgotten my cable release that day. So much for the theory you do not need an expensive 10x loupe to assess critical focus because only the center counts…

Update (2012-02-10):

In 2007 I added a Calumet-branded 4x Rodenstock aspheric loupe to my collection. Unfortunately, it is now only available under the original brand, for 2.5x the price I paid for the rebranded one, but you may luck out and find old-new stock at you local Calumet Photo store. The market for loupes has mostly evaporated, along with the popularity of film, and choices today are pretty much limited to Schneider and Rodenstock.

The Rodenstock 4x loupe has one great ergonomic feature: instead of interchangeable clear and dark screw-in skirts, it has a clear skirt and a sliding dark outer skirt. This allows you to switch very quickly from inspecting prints to slides, without the laborious swap the Schneider or Zeiss force you into. Optically it is excellent, sharp across the field and with only a smidgen of pincushion distortion. I have not tried the 4x Schneider loupe, which gets rave reviews, and cannot comment on whether the ergonomic improvement in the Rodenstock warrants a 50% premium in street price over the Schneider.

One loupe I cannot recommend, on the other hand, is the Leica 4x magnifier. It has severe distortion across the field, which is ridiculously limited at 3 or 4mm, and optical quality is worse than a cheapo plastic loupe from Peak.

Update (2012-02-25):

I added a Schneider 4x loupe to my collection. Build quality and strap is similar to their 10x loupe. It is sharp across the entire frame, with only a smidgen of pincushion distortion. It is also noticeably brighter than the Zeiss Triotar or the Rodenstock 4x, and has more contrast as well. The contrast makes it seem superficially sharper than the Zeiss or Rodenstock, but examination of the Edmunds test chart shows all three loupes outresolve the chart.

I think this will be my new favorite loupe for 35mm use.

Deborah Copaken Kogan

Random House, ISBN: 0375758682  Publisher, Buy online

I picked up the hardcover edition of this book from the sale bin at Stacey’s Booksellers, as the Leica on the cover just beckoned to me.

This is an autobiography by an American woman, almost a girl, who moved to Paris, fresh out of college, to break into the tightly-knit (and not a little macho) community of photojournalists. Who knows, I might even have crossed paths with her when I studied in Paris. She was certainly not the first female war correspondent, Margaret Bourke-White springs to mind (even though she is not referred to anywhere in the book), but women were still a rarity, specially one as young and inexperienced. She started as a freelancer and eventually ended up working for the Gamma agency, one of the few independent photo agencies left.

For some unknown reason, many of the prestigious photo press agencies are based in Paris, starting with Magnum, founded simultaneously in Paris and New York by Robert Capa (the man who took the only photographs of D-Day), Henri Cartier-Bresson, George Rodger and Chim Seymour. Others like Gamma, Sygma and Sipa followed, but most have been acquired since by large media conglomerates like Bill Gates’ Corbis. The move to digital, with the corresponding explosion in equipment costs is one reason – the independent agencies simply couldn’t compete with wire services like Reuters or Agence France Presse (AFP), the latter being government-subsidized. Saturation is probably another, and press photographers struggle to make a living in a world with no shortage of wannabes. Just read the Digital Journalist if you are not convinced.

Shutterbabe is not a mere feminist screed, however. Engagingly written, with very candid (sometimes too candid) descriptions of the sexual hijinks and penurious squalor behind her trade, this book is a pleasurable read and features a varied rogues’ gallery ranging from the cad (her first partner) to the tragically earnest (her classmate who is executed by Iraqi soldiers while covering Kurdish refugees). It only touches in passing on photographic technique, as the general public was clearly the intended audience, but more surprisingly, does not include that many of her photos either. The main thread reads like a coming of age story, with the young (25 year old at the time) woman moving on from her thrill-seeking ways and discovering true love and marriage in a life marked by death: deaths of friends and colleagues, victims of strife and war in Afghanistan or Russia, but also orphans dying of neglect in Romania.

A photojournalist is always in a rush to get to the next assignments, and she recognizes her involvement with her subjects’ culture as superficial, unlike that of her locally based correspondent colleagues or those who would nowadays be called photoethnographers. There is more humanity in a single frame by Karen Nakamura or Dorothea Lange than in all of Deborah Copaken’s work. Much like her idol Cartier-Bresson’s work, there is a certain glib coldness, perhaps even callousness to her attitude. On her first war coverage, an Afghan who is escorting her (so she can make her ablutions in privacy) has his leg blown off by a landmine, and she hardly elicits any concern for the poor soul. Granted, this is the “Shutterbabe”, not the reborn Mom. but it is hard to imagine one’s fundamental personality changing that much.

The author is not uncontroversial. She featured in a nasty spat with Jim Nachtwey, one of the most famous photographers alive, and who is obliquely referred to in Shutterbabe‘s Romanian chapter (where she implies she found out first about the terrible situation in the orphanages, and nobly tipped him so the story could come out). The follow-ups are here and here.

Her observations of the one culture she is immersed in, the French one, seldom go beyond the realm of cliché. Glamorous but feckless and chauvinistic Frenchmen! Sexpot Frenchwomen! Narcissistic French intellectuals!

In the end, she returns to the United States with her husband, and moves into an equally short-lived career in TV production to support her family. A happy ending? One hopes. I for one am curious about how her children will react to the book when they are old enough to read it.

Many digital photographers (including myself) prefer shooting in so-called RAW mode. In theory, the camera saves the data exactly as it is read off the sensor, in a proprietary format that can later be processed on a PC or Mac to extract every last drop of performance, dynamic range and detail from the captured image, something the embedded processor on board the camera is hard-pressed to do when it is trying to cook the raw data into a JPEG file in real time.

The debate rages between proponents of JPEG and RAW workflows. What it really reflects is two different approaches to photography, both equally valid.

For people who favor JPEG, the creative moment is when you press the shutter release, and they would rather be out shooting more images than slaving in a darkroom or in front of a computer doing post-processing. This was Henri Cartier-Bresson’s philosophy — he was notoriously ignorant of the details of photographic printing, preferring to rely on a trusted master printmaker. This group also includes professionals like wedding photographers or photojournalists for whom the productivity of a streamlined workflow is an economic necessity (even though the overhead of a RAW workflow diminishes with the right software, it is still there).

Advocates of RAW tend to be perfectionists, almost to the point of becoming image control freaks. In the age of film, they would spend long hours in the darkroom getting their prints just right. This is the approach of Ansel Adams, who used every trick in the book (he invented quite a few of them, like the Zone System) to obtain the creative results he wanted. In his later days, he reprinted many of his most famous photographs in ways that made them darker and filled with foreboding. For RAW aficionados, the RAW file is the negative, and the finished output file, which could well be a JPEG file, the equivalent of a print.

Implicit is the assumption that the RAW files are pristine and have not been tampered with, unlike JPEGs that had post-processing such as white balance or Bayer interpolation applied to them, and certainly no lossy compression. This is why the debate can get emotional when a controversy erupts, such as whether a specific camera’s RAW format is lossless or not.

The new Nikon D70’s predecessor, the D100, had the option of using uncompressed or compressed NEFs. Uncompressed NEFs were about 10MB in size, compressed NEF between 4.5MB and 6MB. In comparison, the Canon 10D lossless CRW format images are around 6MB to 6.5MB in size. In practice, compressed NEFs were not an option as they were simply too slow (the camera would lock up for 20 seconds or so while compressing).

The D70 only offers compressed NEFs as an option, but mercifully they have improved the performance. Ken Rockwell asserts D70 compressed NEFs are lossless, while Thom Hogan claims:

Leaving off Uncompressed NEF is potentially significant–we’ve been limited in our ability to post process highlight detail, since some of it is destroyed in compression.

To find out which one is correct, I read the C language source code for Dave Coffin’s excellent reverse-engineered, open-source RAW converter, dcraw, which supports the D70. The camera has a 12-bit analog to digital converter (ADC) that digitizes the analog signal coming out of the Sony ICX413AQ CCD sensor. In theory a 12-bit sensor should yield up to 2¹² = 4096 possible values, but the RAW conversion reduces these 4096 values into 683 by applying a quantization curve. These 683 values are then encoded using a variable number of bits (1 to 10) with a tree structure similar to the lossless Huffmann or Lempel-Ziv compression schemes used by programs like ZIP.

The decoding curve is embedded in the NEF file (and could thus be changed by a firmware upgrade without having to change NEF converters), I used a D70 NEF file made available by Uwe Steinmuller of Digital Outback Photo.

The quantization discards information by converting 12 bits’ worth of data into into log₂(683) = 9.4 bits’ worth of resolution. The dynamic range is unchanged. This is a fairly common technique – digital telephony encodes 12 bits’ worth of dynamic range in 8 bits using the so-called A-law and mu-law codecs. I modified the program to output the data for the decoding curve (Excel-compatible CSV format), and plotted the curve (PDF) using linear and log-log scales, along with a quadratic regression fit (courtesy of R). The curve resembles a gamma correction curve, linear for values up to 215, then quadratic.

In conclusion, Thom is right – there is some loss of data, mostly in the form of lowered resolution in the highlights.

Does it really matter? You could argue it does not, as most color spaces have gamma correction anyway, but highlights are precisely where digital sensors are weakest, and losing resolution there means less headroom for dynamic range compression in high-contrast scenes. Thom’s argument is that RAW mode may not be able to salvage clipped highlights, but truly lossless RAW could allow recovering detail from marginal highlights. I am not sure how practicable this would be as increasing contrast in the highlights will almost certainly yield noise and posterization. But then again, there are also emotional aspects to the lossless vs. lossy debate…

In any case, simply waving the problem away as “curve shaping” as Rockwell does is not a satisfactory answer. His argument that the cNEF compression gain is not all that high, just as with lossless ZIP compression, is risibly fallacious, and his patronizing tone out of place. Lossless compression entails modest compression ratios, but the converse is definitely not true: if I replace the file with a file that is half the size but all zeroes, I have a 2:1 compression ratio, but 100% data loss. Canon does manage to get the close to the same compression level using lossless compression, but Nikon’s compressed NEF format has the worst of both world – loss of data, without the high compression ratios of JPEG.

Update (2004-05-12):

Franck Bugnet mentioned this technical article by noted astrophotographer Christian Buil. In addition to the quantization I found, it seems that the D70 runs some kind of low-pass filter or median algorithm on the raw sensor data, at least for long exposures, and this is also done for the (not so) RAW format. Apparently, this was done to hide the higher dark current noise and hot pixels in the Nikon’s Sony-sourced CCD sensor compared to the Canon CMOS sensors on the 10D and Digital Rebel/300D, a questionable practice if true. It is not clear if this also applies to normal exposures. The article shows a work-around, but it is too cumbersome for normal usage.

Update (2005-02-15):

Some readers asked whether the loss of data reflected a flaw in dcraw rather than actual loss of data in the NEF itself. I had anticipated that question but never gotten around to publishing the conclusions of my research. Somebody has to vindicate the excellence of Dave Coffin’s software, so here goes.

Dcraw reads raw bits sequentially. All bits read are processed, there is no wastage there. It is conceivable, if highly unlikely, that Nikon would keep the low-order bits elsewhere in the file. If that were the case, however, those bits would still take up space somewhere in the file, even with lossless compression.

In the NEF file I used as a test case, dcraw starts processing the raw data sequentially beginning at an offset of 963,776 bytes from the beginning of the file, and reads in 5.15MB of RAW data, i.e. all the way to the end of the 6.07MB NEF file. The 941K before the offset correspond to the EXIF headers and other metadata, the processing curve parameters and the embedded JPEG (which is usually around 700K in size on a D70). There is no room left elsewhere in the file for the missing 2.5 bits by 6 million pixels (roughly 2MB) of missing low-order sensor data. Even if they were compressed using a LZW or equivalent algorithm the way the raw data is, and assuming a typical 50% compression ratio for nontrivial image data, that would still mean something like 1MB of data that is unaccounted for.

Nikon simply could not have tucked the missing data away anywhere else in the file. The only possible conclusion is that dcraw does indeed extract whatever image data is available in the file.

Update (2005-04-17):

In another disturbing development in Nikon’s RAW formats saga, it seems they are encrypting white balance information in the D2X and D50 NEF format. This is clearly designed to shut out third-party decoders like Adobe Camera RAW or Phase One Capture One, and a decision that is completely unjustifiable on either technical or quality grounds. Needless to say, these shenanigans on Nikon’s part do not inspire respect.

Generally speaking, Nikon’s software is usually somewhat crude and inefficient (just for the record, Canon’s is far worse). For starters, it does not leverage multi-threading or the AltiVec/SSE3 optimizations in modern CPUs. Nikon Scan displays scanned previews at a glacial pace on my dual 2GHz PowerMac G5, and on a modern multi-tasking operating system, there is no reason for the scanning hardware to pause interminably while the previous frame’s data is written to disk.

While Adobe’s promotion of the DNG format is partly self-serving, they do know a thing or two about image processing algorithms. Nikon’s software development kit (SDK) precludes them from implementing those algorithms instead of Nikon’s, and thus disallows Adobe Camera RAW’s advanced features like chromatic aberration or vignetting correction. Attempting to lock out alternative image-processing algorithms is more an admission of (justified) insecurity than anything else.

Another important consideration is the long-term accessibility of the RAW image data. Nikon will not support the D70 for ever — Canon has already discontinued support in its SDK for the RAW files produced by the 2001 vintage D30. I have thousands of photos taken with a D30, and the existence of third-party maintained decoders like Adobe Camera RAW, or yet better open-source ones like Dave Coffin’s is vital for the long-term viability of those images.

Update (2005-06-23):

The quantization applied to NEF files could conceivably be an artifact of the ADC. Paradoxically, most ADCs digitize a signal by using their opposite circuit, a digital to analog converter (DAC). DACs are much easier to build, so many ADCs combine a precision voltage comparator, a DAC and a counter. The counter increases steadily until the corresponding analog voltage matches the signal to digitize.

The quantization curve on the D70 NEF is simple enough that it could be implemented in hardware, by incrementing by 1 until 215, and then incrementing by the value of a counter afterwards. The resulting non-linear voltage ramp would iterate over at most 683 levels instead of a full 4096 before matching the input signal. The factor of nearly 8 speed-up means faster data capture times, and the D70 was clearly designed for speed. If the D70’s ADC (quite possibly one custom-designed for Nikon) is not linear, the quantization of the signal levels would not in itself be lossy as that is indeed the exact data returned by the sensor + ADC combination, but the effect observed by Christian Buil would still mean the D70 NEF format is lossy.