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I've been trying to render a scene with a dark infinite background, but when I use a vignette effect it looks posterized. I thought that it might be something I did in my Blender file, but then I started a new file just to test it and it seems like that's the way it works...

Bright background (no posterize effect)

enter image description here

Dark background (posterized)

Open the image to visualize it better

enter image description here

I tried adding a blur filter but it makes it worst:

enter image description here

Blend file: https://drive.google.com/file/d/1pIytoPHVPMyP7YvvJW72glZ9j9wP4Kz5/view?usp=sharing

Felipe Del Rio
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  • One of the reason -why it is not visible on brighter and visible on darker is probably because darker has smaller color range of steps to display fade seamlessly. But since blender renders in Linear without loosing any colour depth it does not make sense either. Hmm – vklidu Jun 28 '20 at 17:13
  • @vklidu we see much more detail in darker values and less in brighter ones (hence the need to assign more bits to darker areas than bright ones) . The issue is not on the render, and you can preserve the subtle tones using 16 bit or more per color , but even then, when viewed in an 8 bit monitor, the banding will come back. – susu Jun 28 '20 at 17:17
  • @susu that is what I tried to say, but I was wrong with render part , you are right with display monitor issue. Thanks :) – vklidu Jun 28 '20 at 18:47

1 Answers1

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What you are experiencing is a quantization error called banding.

Most monitor can only display 8 bits per color or 256 tones from dark to bright. There are just not enough levels to do a subtle gradient between two dark tones or similar colors.

It is a limitation that will show in most monitors (unless you have one that can do 10 bit display).

As a workaround, you can play with the dither settings in the Post Processing settings for the scene.

(from the blender Manual)

Dithering

Dithering is a technique for blurring pixels to prevent banding that is seen in areas of gradients, where stair-stepping appears between colors. Banding artifacts are more noticeable when gradients are longer, or less steep. Dithering was developed for graphics with low bit depths, meaning they had a limited range of possible colors.

enter image description here

vklidu
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susu
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    Dither is applied to final render in Image Editor, but not to the "Backdrop" of Node Editor – vklidu Jun 28 '20 at 18:54
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    @vklidu indeed, for the preview window there is nothing that can be done. The rendered image can be dithered. It is a postproduction process. – susu Jun 28 '20 at 19:48