Notes on the future of Open RAW formats, and a look at DNG (by Stuart Nixon)

[Legal preamble - these are my own opinions only. I welcome and will happily publish valid corrections.]

Good morning.

There seems to be some confusion about DNG. Speaking both as a software developer and a photographer (and having had a lot to do with patent issues and image standards like JPEG 2000), I'd like to add my $0.02 to the debate.


Let me first make one thing clear: DNG is not an open standard for defining and storing all needed RAW camera information.

DNG makes the RAW format problem worse, not better.

DNG is not an open standard in that it does not document all the essential information contained in current RAW format files like NEF and CR2 (which also don't document this information).
In many ways, DNG can be viewed as simply yet another RAW format with undocumented information - except that DNG has the added risk that information can be lost during conversion to/from DNG and other RAW formats.
From a software developer point of view, DNG is a step backwards. From a camera manufacture's perspective, DNG does not address the missing elements in EXIF.
From a photographers perspective, DNG is dangerous because people believe they are storing for the future with the format, when nothing could be further from the truth.


A quick recap of the current state of the RAW format market is in order:

  • Aldus defined the TIFF 6.0 specification in 1992. Aldus was taken over by Adobe, who now control the format specification.
  • TIFF uses an extendable structure called IFD, which stands for Image File Directory. This makes it possible to add new content to TIFF files, and allows other formats like JPEG to be embedded into TIFF. The TIFF IFD structure can also be embedded into other formats like JPEG.
  • There are many, many sub-variations of TIFF, to the point that no one product (including Adobe's own products) reads and writes all the TIFF variations and permutations. And this is just for official TIFF format files - no product comes even close to reading all the different extended versions.
  • TIFF has many technical problems including being hard to implement, no standard support UNICODE support and limited to 2GB file size. Various hacks exist to address some of these issues, making technical consistency even worse.
  • Over the years, sub-variations, standards and extensions to TIFF were created by different groups. Some of the more important ones are:


  • IFD
Stuart Nixon – Mon, 2006/04/03 – 10:00am
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