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Topics - cpc

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Most of you are probably familiar with losslessly compressing DNG raw video with DNG Converter. The compressed DNG sequences work fine in both Resolve and ACR.
I've written a small tool (DNGStrip) to strip these of useless stuff which is unconditionally added by DNGConverter to each frame: a thumbnail and some pointless tags. Mac and Windows versions, free to use. Pretty fast. Download link in this article: Lossless compression for DNG raw video + introducing DNGStrip. The text also gives more context on the whole process.

In short, compressed 16:9 frames will lose 114kb per frame, compressed 2:1 frames will lose 102kb per frame after going  through DNGStrip. Test footage (2:1 1920x960 Canon 5dm3 raw) was reduced from 710gb to 399gb with DNG Converter and then further down to 377gb with DNGStrip. That's 53.1% of the original size for full original image quality and average bitrate only 317 mbps. Not bad, methinks.

I'm preping to start doing some post on a few months old raw project shot on 5dm3 and I was checking the DNG files I got. Off-the-camera files were converted with RAWanizer.
What strikes me as odd is that in the resulting .dng files the tag for ColorMatrix1 uses the daylight (D65) matrix, but the corresponding CalibrationIlluminant1 tag is Standard Light A (Tungsten).
There is also no ColorMatrix2 tag, although there is a CalibrationIlluminant2 tag (D65). I had a quick look at the source code and it appears this is coming from raw2dng and not from RAWanizer.

If you wonder what the visual effect of these matricies is in a raw processing software: there is subtle tint movement mostly over the green-magenta axis, but also skin moves subtly from yellow to pink. This can be verified in ACR or Resolve.

I can fix this easily with exiftool, and also add the second color matrix to my files, but before doing this I wonder if there is a specific reason for what looks like a mismatch in the values used in these tags? Thanks.
(I wasn't sure if this is the correct subforum for the question, pls move the post if appropriate)

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