"As shot to reference" in white balance module

RawConvert · March 20, 2024, 5:44pm

Using a recent nightly DT appimage, 4.7.0 761, I’m seeing a new item in the settings dropdown, namely “as shot to reference”. Anyone know what this is about please?

priort · March 20, 2024, 7:26pm

Some modules work better with as shot wb data so it is used for those then the reference values are used to work with the CC module.

github.com/darktable-org/darktable

Revamp D65 chroma correction workflow

darktable-org:master ← jenshannoschwalm:temp_and_chroma

opened 08:20AM - 21 Oct 23 UTC

jenshannoschwalm

+503 -343

With the modern scene-referred workflows we do chroma correction in three parts:… 1. We use the 'camera reference' data found in temperature module assuming they are D65 2. translate what we have to working profile in 'input color profile' 3. Do a "refinement step" in color calibration assuming we had D65 in step 1 This leads to improved color data in follwing modules - thus it was introduced. Unfortunately there are some downsides from this approach. Some modules want accurate white balance data for best quality, most notably highlights and raw ca correction. Both modules modify data found in the rgb channels towards "best guessed white" but can't do so as those data are currently not available. This PR implements a chroma struct in dev (like a proxy) holding all required and available white balance data for the current image (D65, as_shot and currently used) allowing runtime a) check - are we using D65? b) access of modules to the other coeffs for improved results c) easier and safe checks for chroma correction related trouble messages EDIT: (25.10) temperature modules gets a button introducing this mode and colorin does the "late correction". Fixes #14518 Related to #15121 and discussions about highlights & opposed

RawConvert · March 20, 2024, 11:28pm

Thanks. I’ve had a look, and the two chained items. I’ve left a comment about using Unity White Balance ETTR shooting because As Shot gives a green image (and the new option seems to be the default for scene-referred). My 2p worth anyway.

priort · March 21, 2024, 2:16am

Sorry I don’t follow… as shot standard WB looks fine in general…just have to turn off CC module…

THen you can do either the older way reference or the new blended and turn cc back on and basically looks fine too… where are you getting the green image from??

Sorry I didn’t find your comment…

Ah are you talking about if you use Unity WB??

Donatzsky · March 21, 2024, 12:11pm

You can still create your own WB coeffs and load them with a preset.

kofa · March 21, 2024, 1:17pm

One can set the camera to use RGB multipliers of 1. Search for UniWB. That produces green images (including in-camera JOGs). I think that’s what Andrew also uses.

priort · March 21, 2024, 2:39pm

Thanks. I started to think that was what he meant but then it still wasn’t clear to me. Was the new mode messing with his workflow… Anyway I wasn’t sure what the actual issue was from his comments and I couldn’t find the note he mentioned…

RawConvert · March 22, 2024, 11:44pm

There are 3 items about this in github, two are closed. #15602 is open and I’ve been having a discussion with @Jens-Hanno_Schwalm there. I still need to ask a bit more, tomorrow probably.