Great shot! Thanks for sharing it with us!
Here’s my rendition using darktable 4.0:
_7230057.ORF.xmp (21.2 KB)
After adjusting exposure, I did the following (roughly):
First, I did an auto color balance adjust in the color calibration module and then manually adjusted it until it looked “about right” to me (since I wasn’t there and you don’t have some color reference shot available, it’s the best I’ve got ).
Then, I made a new color calibration module module above that and heavily adjusted the blue channel’s brightness down and compensated with a touch of red and a little more green, to bring the brightness where I wanted it.
After, I adjusted filmic, added two copies of the “diffuse or sharpen” module (first: to heavily sharpen the lens blur, second: adding a bunch of local contrast). Apologies if this makes it super slow for anyone trying out the file. (OpenCL is great for this, when you have a good GPU.)
Then, I boosted the color with color balance rgb (“vividness”) and then toned the colors a bit more to my liking in a separate color balance rgb (“color grading”). The grading pass was mainly to control colors a bit, so they’re not extremely out of gamut, and to balance the red vs. blue cast a bit.
While this is a lot, the largest changes were in the two copies of “color calibration”. Getting the approximate colors you want goes a long way and adjusting the channels to darken the blue (since it’s so bright underwater) makes the image have the effect you see here. It’s a good method for darkening blue skies too (simulating a polarizer a bit and increasing the contrast of a blue sky with clouds), by-the-way.
As “diffuse or sharpen” is such a heavy module and I use it twice, I’ve made a version that uses the “sharpen” and “local contrast” (with a mask to protect dark and light, plus to target sharper parts of the image, with some feathering) for those of you who may not have powerful enough computers (I was one of you until a few months ago)… and also to compare how awesome “diffuse or sharpen” is compared to the standard sharpen and local contrast modules. (You can see haloing from the normal local contrast module, even with the mask, and the sharpen module isn’t as optically correct.) It’s not intended to be a perfect 1:1 comparison, but something rather close. Look around the halos of the fish (especially the zebra fish) in the second picture versus the first (which doesn’t have this). Aside from these two replacement modules, everything else is identical.
_7230057_01.ORF.xmp (10.5 KB)