Corona Sky Color Banding issue

[JuL]

Hi there,

Is the Corona dev team still investigating about the color banding issue on corona sky map ?
If so, can you share some informations because for now on that feature as become nearly useless (unless a lot of time-consuming post production...).

Thanks for you feedback

(image produced in 3ds max 2025.3 / Corona 13)

[pokoy]

Are you saving to a file that only supports 8 bits? In that case it's expected, as there are too few numeric values to represent a smooth transition in 8 bits. The only thing that'll help in that case is adding some noise. You should see no banding if you save to a format that supports 16 bits or more, e.g. 16 bits TIF or EXR.

[JuL]

Hi and thanks for your reply,
Unfortunately these bandings appears also on 32 bits .exr saved files, the attached jpg was just a lighter way to show the issue.

[pokoy]

I don't think it can be avoided since you're probably going to deliver it in 8 bits anyway. Try adding noise/grain to the image or background, it should help.

[zeropluszero]

Hello, i am facing the exact same issue, and that is very, very, annoying :)
To add some precisions, saving the file in 16/32 bit EXR and then convert it from a software to a 8 bit jpg works, you dont have those "bandings".
But for an unknown reason, while the VFB is in 32bit, saving it directly to the jpg create them ....
Would any dev be able to have a look, hoping the VFB could behave just like a "photoshop's like" program and cleanly convert to 8bit ?
Or maybe we dont understand well the issue there ?
In any case, that is really an issue making procedurals, and especially corona skies, useless.

Thanks in advance !

edit : here's an example, on the left, the image is saved straight to 8bit from the VFB, on the right converted 16bit to 8bit ... so no "8bit" issue there ...

[romullus]

Would any dev be able to have a look, hoping the VFB could behave just like a "photoshop's like" program and cleanly convert to 8bit ?
Or maybe we dont understand well the issue there ?

Actually Photoshop is doing opposite of "clean" convert, the reason you don't see the banding after converting the image from 16 bit to 8 bit is because Photoshop is adding some noise (it's called dither). If you'd adjust levels on converted image, you can see that banding is largely still there, but is masked by noise, which makes the banding almost imperceptible to human eye.