It seems to show up when I add the Local Adjustments Sharpening tool to a spot but this is clearly not a problem with RawTherapee because I never saw this on my old laptop (which had an Nvidia card)
I can confirm the bad behavior with both a JPEG and RAW file. This seems an unwanted interplay between the Contrast by Detail Levels and the Sharpening module for Local Adjustments. The effect gets progressively worse by increasing the contrast in CbDL.
@jdc Are you able to take a look at what is going on?
Edit: it only happens in “Before Black-and-White” mode.
Thanks for looking into it Jacques. It might be something as easy as a 0-value somewhere after CBDL that does not work well with the sharpening module.
I think now would be the ideal time to fix a bug so that we can ship 5.9 with one bug less