Inside Adobe's New Digital Negative Format

When Adobe speaks about camera raw problems, people listen. And the software giant spoke loudly on Monday when it released an update to the free Camera Raw plug-in for Photoshop CS. The plug-in update adds support for a new Adobe-proposed file format for digital negatives—a clever marketing name the company wants to use to replace the less-friendly camera raw .

All About Raw

What are digital negatives? Most digital cameras don’t record full-color information that's ready to send to your computer through a simple binary dump. The imaging devices behind the lens typically only capture grayscale data at best, with color filters over some of them so they only record light of a particular color. The camera’s firmware takes this “raw” data, assigns color to the pixels through knowledge of the filters in place, combines it with your settings, and creates a full color image. It then compresses that image in the JPEG format and sends that to your computer.

In traditional photography terms, if a JPEG image is the developed picture, the raw data used to create it is the photographic negative - the digital negative, as it were. If you were to reprocess the raw data using different settings or algorithms for white balance, color interpretation, gamma correction, noise reduction, sharpening, or any of several other properties, you’ll get a different image. Access to the raw data and capable software lets you play with those parameters, just like a photographer might print a negative in different ways to achieve different effects (as imaging expert Bruce Fraser explains in this downloadable white paper ).

It takes a comprehensive program to manipulate all the appropriate parameters and algorithms to do something meaningful with raw data. Because camera makers each invent their own ways to store raw data—with a single manufacturer sometimes using different “raw” formats for different cameras—software that wants to interpret “camera raw” has to know all of the formats, and keep up with new ones as they’re invented and released.

Adobe’s Role

Adobe wants camera makers and others with interest in raw data to stop reinventing the wheel and use a standardized format, and who better to propose one than Photoshop’s developers? Adobe Photoshop reigns as the undisputed leader for interpreting camera raw data. If photographers don’t use Photoshop itself to read their raw data, they almost certainly use it afterwards to manipulate the results.

Adobe’s new DNG file format is a nonproprietary extension of the raw-oriented TIFF-EP file format, itself an extension of the TIFF 6.0 format that Adobe maintains and controls (because TIFF was invented by Aldus, and Adobe purchased Aldus more than a decade ago).

The 40-page specification details how the DNG format expands upon TIFF, including restrictions on existing TIFF-EP tags. It also describes some 38 new tags to store all the camera-specific information a program needs to interpret the raw data, including camera calibration, white and black points, noise reduction, lens information, and even camera information such as name, localized name, and serial number. There are ways for camera makers to store private data that the camera may need, but even so, DNG files should still be recognizable as TIFF-EP files, even though TIFF-EP readers may not provide the best conversion from raw data to processed images.

If camera manufacturers adopt Adobe’s Digital Negative file format, they’ll be sure that Adobe Photoshop can always read and manipulate their camera’s raw data, and that any other programs who adopt the nonproprietary format can do the same. Adobe also points out that adopting a standard format means that photographers can preserve their digital negatives forever, and not worry about a proprietary format vanishing as the camera or its included software become obsolete.

By driving the format, Adobe ensures that its products will have the most authoritative support for it. The TIFF-EP specification includes EXIF metadata, but since Adobe invented DNG, it made sure to include support for its XMP metadata format as seen in all Creative Suite applications. Adobe also maintains control, for DNG is a nonproprietary file format, not an open one. As with PDF, TIFF, “.psd”, and other formats that Adobe controls, only Adobe can officially change the DNG specification.

A file format is a theoretical benefit until software starts using it, so Adobe kicked off its initiative by releasing the Camera Raw 2.3 plug-in for Photoshop with support for DNG files. Adobe offers packages in English and Japanese that also come with the new Adobe DNG Converter, an application that converts any of the “camera raw” formats that Adobe knows about into the new DNG files. The Camera Raw plug-in is also available without the converter application in English, and in a separate version for Chinese, Japanese, and Korean systems. It adds support for the Canon PowerShot S60, Fujifilm FinePix S20Pro, Epson R-D1, and Nikon CoolPix 5400 cameras, as well as the new DNG format.

Excerpted with permission from the September 29 issue of MDJ, published by MacJournals.com. Copyright 2004, GCSF Incorporated. For a free trial to MDJ, visit www.macjournals.com.

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