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I see a few fundamentals

I see a few fundamentals issues with the article.

1. The most important is that the author does not seem to have looked at the DNG spec 1.2 very closely. There were several important changes incorporated in that document that make the format considerably more friendly to third parties. These include:
a. Provisions for any software to attach its color decoding profiles into the DNG, even if they are entirely different than those used by Adobe.
b. A tag was added to indicate which application built the embedded rendering. This was added specifically because users will have DNG files created by different applications, and need to send them for output and get predictable results.
c. The licensing terms for Adobe's color matrix was updated to address concerns of third-party software, and licensing terms were added to enable third-party software to protect or distribute its own rendering profiles, if they so choose.

2. The article makes two claims about the rendering differences produced by DNG files processed by Adobe software. In the first, the author uses "an old version of the DNG converter." It would be helpful to know which one. Is it the first implementation, or a later one? There were acknowledged problems with the very first version that have been rectified in later versions. And what does "amplified" mean, exactly?

In the second claim, the author states that the renderings produced by different versions of Camera Raw are, in fact, somewhat different. This is pretty unsurprising, since the current software has had further engineering, and refinements to the rendering engine. For the comparison to be of real value, the author should document how he has created and applied the parametric rendering instructions for the comparison of the files. It's quite likely that the first image is taking advantage of improvements in sharpening and shadow rendering that were built into the later version but not available to version 3.x (he does not document which versions he used to test with). The 5.x version is also highly likely to be using a different profile to render, although he could choose to use the old one if he wishes.

Either the author tested in the manner he did to purposely skew the results, or he does not understand rendering and forward compatibility very well. For instance, it would be much more relevant to know if a DNG made in ACR 3.6 looked the same when rendered out of 5.2, and what rendering instructions were present. The method he chose will clearly employ the improvements in the current version when rendering the file, including sharpening, vibrance, new profiles and other rendering tools. These will not be available in all past versions, just as some TIFF layer adjustments from Photoshop CS3 can't be understood by Photoshop CS, and so a different result will be produced. At minimum, this needs to be understood.

Most importantly, the author's criticism's here seems to be confused by the capabilities of the specification, and Adobe's implementation of the spec. He also does not seem to understand that the universality of DNG is that of a container, not a particular rendering. The *only* way to get a universal static rendering of the file it to embed a non engine-specific one: this has also been greatly enhanced by the tools in the 1.2 spec, which the author should take some time to try and understand. This kind of unclear thinking, along with sloppy research from the primary documents, does not move the discussion forward.

I would be interested in hearing specific suggestions regarding these issues, if they are informed by clear thinking about what is the job of the specification, and what is the job of the software, and how to handle forward compatibility in a parametric image editing environment. While there are surely a number of important issues to address - I can think of at least a half a dozen - very little in this article approaches that.

Peter Krogh
Author, The DAM Book, Digital Asset Management for Photographers