Ugly circles when adding a vignette to a JPEG

Software RawTherapee
1

I try to add a vignette to my JPEG in GIMP (with a new layer soft light).
But when I pixel peep I see ugly circles in parts of the sky.

Then I try the same with Rawtherapee: Open my JPEG in Rawtherapee, add a vignette and export the photo to JPEG (100% quality).
But then I see the same ugly circles.

All the other editing of my JPEG in RawTherapee gives me very good high quality results.
Only the vignette destroys the quality often!

Do you have any tips for me?
How can I get good quality vignettes in RawTherapee or GIMP all the time?
Thanks!

2

@leendertv upload the source file and show screenshots of the problem.
Though it sounds like your problem has nothing to do with RawTherapee since you get the same “ugly circles” using GIMP.

3

Without an example this is a guessing game.

My guess is that your problem is banding due to the 8 bit display. I’m just surprised that you only see it after exporting.
To reduce the problem try dithering the output and saving it as a really high quality jpeg.
I’m not sure if RT supports dithering but Gimp certainly does. Export as 16 bit tiff. Open it in a dev version of gimp with support for high bit depth. Then image/precision/8 bit and select random (resilient would be even better in your case but it looks like it has been removed.

http://fhotolab.fherb.de/2016/09/04/dithering-ein-gimp-tutorial/ << is a tutorial in German but you can probably follow it just from the screenshots.

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4

You are right! The banding in RT is only a problem when exporting to an 8bit JPEG!
Perhaps this is a possible improvement for RT?

The pictures in the german tutorial shows exactly my problem and a good solution.

I found an other solution in GIMP: https://docs.gimp.org/en/plug-in-spread.html
Filters → Noise → Spread
spreading amount: 10

Thanks!

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5

The best kind of diagnosis is self-diagnosis followed by self-medication.

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