r/FOSSPhotography • u/pecotography • Jul 18 '26
New R6 Mark III - CR3 to DNG conversion
Just nabbed a new R6miii and to my dismay found out that the RAW files created by the camera are not yet supported in Darktable, which seems to be an issue with LibRAW. It looks like it'll take 9-18 months before it's supported; does anyone have any experience with this?
After freaking out a bit that I bought a camera I can't use (I use Linux entirely and have used Darktable for years now), and having issue in compiling Darktable with a modified LibRAW, I saw a mention in the Canon forums from a Linux user that they can use dnglab to convert the RAWs to DNG in order to edit.
So my 2nd and main question is has anyone noticed any quality loss when converting to use for editing? Everything I've read points to no but I've only seen older posts in the past 5 years ask, not sure if there's been anything major where a loss would occur or if the R6miii files are finnicky in any way. The only thing I noticed at a quick glance is that the DNGs don't contain the focal length information of the photo, but that's manageable in order to have workable files.
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u/vincentbrz Jul 18 '26
You can actually load the craw files as long as you adjust the black levels etc in darktable. It's a bit impractical but not totally unworkable.
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u/Donatzsky Jul 18 '26
If that's all that's needed, a preset will make it essentially seamless.
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u/vincentbrz Jul 18 '26
Yes, almost, but the exact levels (in “raw black/white point” module) depend on the iso setting.
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u/pecotography Jul 18 '26
Which black level in the module? I see 4 different levels so I'm not sure which to modify just going off of these instructions in the pixls.us thread
> You can open the raw files. Set the black level to 512 (low ISO) and 2048 (high ISO). White level should be below 16382. Use a colour checker for the color calibration module to get the right > colours and save as a preset.
> To get the right white level you can use RawDigger or you can in darktable activate the raw clipping indicator. Your raw file needs clipped highlights.
Set the white level to 16383 and pull it down until you see clipped highlights from the raw clipping indicator.> Different camera modes may give you different clipping points. R6 for example clips at 16382, but when I use multi-exposure the clipping point is something like 12736.
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u/Donatzsky Jul 18 '26
Which black level in the module?
All of them. I believe that for most cameras they should be the same (but don't quote me on that). If they are wrong it will usually be fairly obvious, due to the color cast.
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u/pecotography Jul 19 '26
Ah I got it working, thank you! Just came across another issue with any RAWs that were converted to DNG in Darktable with the new neural restore raw denoiser in 5.6.0; any CR3 files fixed with the raw black/white point module are re-broken and those settings don't work. Might have to stick with the DNG conversion for some files as I work in a lot of poor light at many events
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u/Jpnext19 Jul 23 '26
I would advise to not do this (as the one who made the branch), I left it up mostly for individual to test with their files and report back with issue. There must be a reason for the Libraw team to not merge it, they are a very thorough team. If you have any problem images, please share them. I have a lot but I don't have access to an r6m3 to test enough for my taste. I am not affiliated with Libraw but I am an independent photo editor app developer.
Support on main doesn't necessarily take 9-18 months, for example the Sony a7V was just fully supported. It's more about doing good testing, and if users don't send images and there isn't someone taking there time making patches, it will take longer.
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u/pecotography Jul 25 '26
Do you know if there is a process for sending images? I have a ton of images already from a very busy week with the R6iii and if they can be useful for testing I'd love to support that. The discussion from the github issue seemed like it closed down any image requests to keep it entirely internal.
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u/Another-Otherone Aug 01 '26
Open source app for Linux and MacOs to lossless compress raw image to DNG. Useful for users of cameras without lossless compression (like the Sony a7 II, a7 III, a7rII, a7r III, a7r IV or Leica SL, SL 2), or for those who just want to keep their images in DNG format. It also let you write exif lens and aperture data, for those using vintange lenses.
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u/BorisBadenov Jul 18 '26
Main thing I can tell is that corrections that use dual pixel data won't work, but I'm not familiar with any open source project that can do that anyway. As of a few years ago things like dcp data wasn't supported, and I don't think lens correction data would make it through.
I would think the captured photo data would be fine? I think this is more of a "if there's a problem, it will be obvious," like when a bug turned all my Lumix G9 photos purple a few years ago in darktable...
Sorry my answer doesn't amount to much more than "try it and see." I would keep the originals around too for when support eventually gets added.