Opinion: Adobe's DNG specification is a boon to software writers and smaller camera manufacturers, but the big players might resist it.Will Adobe's DNG (Digital Negative ) displace the current multitude of raw camera formats? I don't really have an opinion, but I can provide some explanatory material to inform the debate.
In a previous column, I said that exposure is easy in digital photography. True, but only true because of the miracle of "Raw."
Raw is an invisible wonder. Photographers rave about the Raw format of their cameras and the exploits of their favorite Raw converters, but prepress never sees a raw image. Adobe's announcement of DNG makes a lot of noise—but no one seems to be writing DNG files—what's going on here?
For now, Raw is a format for photographers only. To simplify matters, Raw is the digital equivalent of a negative. Equivalent? No, it's really, really better! If you have a raw file, you can change the exposure and white balance of a shot considerably, long after you've taken it. This is a lifesaver. It's a miracle. It's real technological progress. It's a genuine innovation that can pay for utility bills and food!
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I'll spare you the micro-details today. Essentially, a Raw file is like color negative film in that it has a large recording range—restated in photographer's jargon, it has very wide latitude. In contrast, slide film and print have a strongly limited range to what they can reproduce.
Now, we can retroactively underexpose or overexpose any shot by almost two stops, no problemo: We employ the Raw converter software to parcel out and "print" a different part of the Raw recording's range, and then write a TIFF or JPEG file. That file gets cropped, retouched, and ultimately sent to press and billed.
If we want more detail in the highlight areas in our final image, we "underexpose" the Raw image at conversion. If we want more shadow detail, we lift the image by "overexposing" retroactively. Yes, there really is an "exposure" slider in Adobe's Raw converter, and others.
It's like using an enlarger to make a print of a negative. The Raw conversion software acts like the enlarger and print developer, except it doesn't stain our fingers!
Where do we get the Raw converter? Major camera manufacturers supply them for free (Canon) or for a reasonable fee (Nikon). There is also a Raw converter built into Photoshop CS and various third-party offerings, the most famous of which is Phase One's Capture One. You can even get free source code for a converter that supports 157 cameras; it's dcraw.c, written by Dave Coffin.
Sure, quality does suffer a bit when adjusting exposure. But the results from Raw adjustments are greatly improved over the results of a curves adjustment in Photoshop, because there is a lot more information in the Raw file.
Now, nailing the exposure during the shoot becomes less critical. Suddenly, exposure bracketing is not a critical necessity, but a luxury to be indulged in when time permits. Thanks to Raw, approximately exposed shots are keepers—I told you Raw pays the bills. Don't you love progress?
Of course, the client never gets to see the Raw image, like she never got to see a negative. By the time the client sees a printable file, the photographer has already enacted the creative choice about which part of the captured image's dynamic range will be "printed," what the color balance will be, and many other fine adjustments. Didn't I tell you Raw was an invisible miracle?
Well, thanks for staying with me this far. Together, I guess we've just about cooked Raw's delicious goose. Let's move on to the second course, Adobe's new DNG format.
Next Page: Taking a close look at Adobe's DNG.
Adobe noted that every camera writes a different Raw format—by necessity, since a Raw file is essentially a binary dump of the camera sensor's Bayer matrix. So, Photoshop, or rather Adobe's "Camera Raw" plug-in, ACR, needed to read zillions of binary file formats—nearly one format per camera model.
With digital camera models breeding faster than rabbits, ACR needed updating at an accelerating pace. So, Adobe got the idea to apply some birth control to the Raw formats by inventing its own "perfect" Raw format. You guessed right, that's DNG.
It's an interesting land-clearing action that Adobe is suggesting, demolishing all the separate formats to erect a unique, overarching DNG. Or is it a land grab? Let's list the presumptive plusses and minuses of DNG.
On the one hand, standardization is good for all software writers. A single open, unified and well-documented format is easier to code for than a zoo of incompatible files.
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Smaller camera manufacturers will also embrace DNG because their clients get instant access to all existing raw converters. Hasselblad and Leica have already bought in.
Customers who like image banks may wish for something like DNG because it provides a unified, long-term archival format.
However, there is one fly in the ointment: Photographic giants such as Kodak, Canon and Nikon may wish to resort to innovative proprietary sensor designs and processing algorithms, which DNG could not immediately embody.
For example, Kodak might have a "Digital Kodachrome" color formula that it would not want to divulge. Canon might have a new noise reduction filter. Nikon could have an innovative lens aberration correction algorithm. Fuji might have a strangely structured sensor whose construction it will not divulge.
Third parties might not feel like licensing their intellectual property to Adobe or others, especially if this would profit their immediate competitors. So there might quickly be a limit to how much of the DNG format a given converter could really process. In the worst-case scenario, the various private formats would simply have become subformats of DNG without losing their proprietary character—separate houses now encircled by a common city wall.
Is the digital camera marketplace already static enough for Raw to be molded into the DNG format? I don't know. You tell me!
Edmund Ronald has a Ph.D. in Applied Mathematics, but he is currently on a sabbatical as a photographer in Paris.
