So the start of the story is that I’m looking for a decent pocket camera and it looks like a choice between the Canon G5X II and the Sony RX100 3/4/5. The Canon looks like it would be much more fun to use, but it suffers from severe blue/purple fringing in the corners at wide angle. Not sure exactly what species of CA this is, but it only affects the corners and cannot be corrected with the channel scaling TCA correction in lensfun. The OOC JPEGs look fine for a compact camera, so it is certainly correctable. Ideally there will be a nice way to it in darktable, but I’m struggling a bit.
Here is an example:
It actually extends maybe 20% into the frame.
The “chromatic aberrations” module in darktable can clean it up quite well:
But this requires both radius and strength to be increased significantly, and there’s a lot of collateral damage, as you would expect (i.e. complete desaturation of small, brightly coloured things across the frame). An elliptical drawn mask that limits the effect to the corners (possibly combined with a parametric mask limiting it to blue things) looks like a pretty good compromise that would work in most cases. Any other ideas for how to tackle it?
The next thing is how to get it into a convenient workflow. My first thought was to create a preset and auto-apply it to images matching the camera and a focal length range, or to create a style and manually apply it. But it looks like drawn mask information can’t be saved as part of a style or preset - the module settings get applied with “drawn and parametric mask” blend mode but no drawn mask. Copying and pasting the history stack does seem to work, though. This isn’t actually too bad a workaround but can anyone see a better way to do it that I’m missing?