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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

DNG is nonproprietary and fully documented. Adobe now supports DNG in a new version of the Adobe Camera Raw plug-in (2.3 and above), which provides integrated support of RAW formats within Adobe Photoshop CS. The format spec is freely and publicly documented, and available for implementation by other vendors. There's no charge of any kind for using DNG for camera manufacturers, software companies or end users. For those who are skeptical of Adobe's intentions regarding DNG, a review of two major file format standards that Adobe already controls—TIFF and PDF—proves that Adobe is willing and capable of maintaining standard file formats for the long term.

DNG is self-contained and self-describing. DNG contains enough publicly documented metadata to allow readers, such as the Adobe Camera Raw plug-in, to adequately decode and process files without prior knowledge of the specific camera model that created the file. This is in stark contrast to the existing situation, where the Adobe Camera Raw plug-in and other software products are unable to process RAW files from new camera models until after their software has been updated.

It should be noted that the quality of the resulting decoding of DNG files would depend on strict adherence to the DNG metadata specifications. The metadata for DNG is critical and the lack of documentation in today's RAW file formats has made current metadata fragile and less practical for photographers. For metadata to attain broad adoption, there must be a way of safely embedding it directly in the RAW files. Unfortunately, with undocumented RAW file formats, this is extremely risky since the location and specifics of the metadata disallow standardized embedding procedures. DNG will resolve these problems by documenting the metadata while still allowing camera manufacturers the ability to include private metadata to be used in proprietary software.

DNG is compatible with existing standards. DNG is an extension to the TIFF-EP format and is compatible with the TIFF 6.0 standard. It's possible for a RAW image file to simultaneously comply with both the DNG specification and the TIFF-EP standard, which already is in wide use and acceptance—it's the basis of many RAW file formats. (References: TIFF 6.0 Specification, Adobe Systems, Inc., 1992-06-03; TIFF/EP Specification, ISO/DIS 12234-2, 1998-11-24.)

DNG supports all current known needs of proprietary formats and can easily be adapted for future needs. By careful format versioning, Adobe can update DNG to take advantage of new technologies while preserving backward compatibility. DNG doesn't hinder creativity and progress with respect to new camera and sensor technologies. In fact, DNG would aid in the development and deployment of technological breakthroughs.
DNG is archival. In contrast to propriety RAW formats, DNG is publicly documented. This makes it far more likely that RAW images stored in DNG will be readable by software in the distant future.


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