I’m still very new to darktable. I have a few wildlife photos that were shot under red torchlight on my recent trip to Tasmania. I’m looking for advice on how to correct this to get a more natural colour, similar to the results in this video:
Attached is one of the images I’d like to edit (Eastern Quoll).
Many thanks for your help in advance!
Shot in Raw with Olympus EM1 Mk2. I have darktable 3.6.0 running on Windows. I also have Gimp v 2.1.24, but I’m even less familiar with that programme as I’ve been more accustomed to using Adobe photoshop CS3 (which no longer works on my laptop).
The hang may be cause by OpenCL. Try disabling it in preferences, under processing.
There’s almost no information in any but the red channel. I don’t think it’s possible to colour-balance this image.
Look at the white balance RGB multipliers when I modified them by hand to get a greyish image:
So it’s not OpenCL. You may try closing darktable, and renaming darktablerc to darktablerc.old to start with a clean setup.
How much memory does your machine have?
Even if it might be possible, you’re going to have a problem where the red and green channels are so severely underexposed that you’re going to have some noise problems.
It looked like the video in question did the following:
Basically treated the red channel as a luminance channel, dropping the green/blue channels because, as you point out, they’re pretty much useless.
Then applied a sepia tone to that greyscale pseudo-luminance channel that was derived from the red channel.
So they now show up ok in the light table view, but the slideshow they are not fully resolving correcty and the slideshow says “working” but is hanging. ETA: there are about 840 GB of pictures (and videos) in the database. So you might be correct.
Did you watch the video…its a few steps including inverting the image… so its not a simple color balance or wb edit but I think most of the steps can be done in dt even though it used layers…
I have a sure fired way of fixing this extreme color cast. Turn off the color calibration module in this case. Just use the white balance module and do a white balance based on a selected area. The white balance module will do a great job. Here is an example where I use this method on a crab photographed under red light. DT is the only program I know of that can do such a dramatic white balance fix. I have tried this image on many programs and only DT has ever worked for me.
EDIT: My method doesn’t work on the supplied image from the original poster. I will continue playing. But my method works for many images and is so easy. Just not this one.
I tried the same as you and it wasn’t bad but I tried to mimic the steps from the video and I couldn’t get the inversion and the blending result to match. I tried with negadoctor followed by a curve and then just some inverted red curve and drop the blue and couple of other things… couldn’t seem to get that step to work as shown in the video… that is far from saying you cant…
Well I have played around with the supplied image and and agree with others that there is next to no information in the red and green channel. I don’t see anyway of bringing back the colors to this image in any program. The crab picture I demonstrated contained information in the blue and green channel and WB could fix the issue, but this image has not colour to recover. I am happy to be proved wrong if anyone can fix the supplied image.
