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Monday, June 18, 2007

The Digital Negative Format

Adobe's proposed standard RAW file format could be the key for the long-term protection and viability of image files



The Promise And Problems Of RAW

Capturing and saving the RAW sensor data of an image allows for far greater flexibility and control over a digital photograph. A RAW file has had little or no processing applied to it so that photographers have the ability to administer their own interpretation of the scene instead of that of the camera manufacturer. The RAW file has the entire full dynamic range and bit depth that the sensor is capable of capturing without the artificial reduction caused by JPEGs. It also provides the entire color space that the camera sensor is capable of capturing without the forced limitations of the camera-processed color gamut. The RAW file isn't restricted to a specific white balance, so postprocessing of the file allows for more precise control. In fact, it's this precise control that's motivating many photographers to use the RAW capture modes in their cameras. Rather than accept the limits imposed by camera-processed files, photographers are using postprocessing in software to determine the critical image parameters. While this gives photographers unprecedented control over their images, it also leads to one of the major problems associated with RAW digital captures—the RAW processing workflow.

Because there has been no historic RAW file format standard, each camera company has had to develop its own proprietary file formats for its cameras. The photographic industry has failed to adopt standards because the rate of change and progress has been extremely rapid. More comfortable with evolutionary changes, the industry was ill-prepared for this revolution because, traditionally, standards were normally the purview of film companies, not camera manufacturers. This situation of nonstandard and generally undocumented proprietary RAW file formats is one of the most serious issues facing the photographic industry today.

Nonstandard proprietary file formats complicate the workflow for photographers, who must use special software just to process the RAW capture into a standard interchangeable file format such as TIFF. Rather than providing flexibility and choices to the photographer, a proprietary file format restricts his or her workflow. Often, different software is required for processing different RAW files from the same camera manufacturer. While the camera companies have shown technical excellence in the development of digital cameras, they haven't exhibited equal excellence in the development of cross-platform software for processing their RAW files. Generally, the proprietary software suffers from a lack of usability, functionality and performance that digital photographers now are requiring for a productive digital processing workflow. This problem is only the tip of a large iceberg.

Orphaned Formats And Future Access To Images

With film, there has been longstanding preservation practices to ensure the archivability of photographic images. The same can't be said for digital photographs. Already some early digital camera file formats have been orphaned and are no longer supported by the companies that produced them. Product cycles that can be measured in months instead of years or decades produce technological advances with little incentive for backward compatibilities. Unless the photographer has access to the special software and computer systems that can operate forgotten file formats, those images conceivably may be gone forever. The proliferation of undocumented and proprietary file formats jeopardizes the long-term archival viability of the digital photographic medium. To make a film-based analogy, imagine if you had to buy only Canon film to use in your Canon camera. That's the analog analogy of RAW file formats—the digital camera makers essentially are doing this when they refuse to adopt a RAW file format standard.

While there are no reasons to assume the camera companies don't honestly intend to continue support of their file formats long into the future, the fact that some RAW file formats already have been orphaned and are unsupported must give the industry pause to consider the role in which camera companies now find themselves. Camera manufacturers traditionally haven't been responsible for the long-term preservation of photographic images; they must now assume that responsibility. Photographers shooting digitally need to be assured that in five, 50 or 500 years from now, their images will be accessible and usable and that the image data contained in their captures—data which is theirs alone—is guaranteed to be archival. Undocumented and proprietary file formats jeopardize long-term viability and must be eliminated for the benefit of the photographic industry.

Adobe has defined DNG to be a format that protects the long-term viability of digital images. It's designed to be a nonproprietary format that can be used by a wide range of camera and software manufacturers to provide a more flexible and fully documented RAW processing and archiving workflow. End users also may use it as an intermediate format for storing image files that were originally captured using proprietary formats. There are a variety of advantages to both the manufacturers and the end user.



 

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