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This is the image with denoiser:

enter image description here

This is the image without the denoiser

enter image description here

Turning on Dither made the image with more noise, like I didn't use the denoiser at all.

Ray Mairlot
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saifart101
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    So, what is your question? – Duarte Farrajota Ramos Apr 19 '19 at 23:33
  • Also, note that z-fighting can be one cause of banding, and you might not recognize it as such if denoising cleans up the render enough that it no longer resembles typical z-fighting you would see in the viewport. (Although I don't think that was the cause in your case, but rather a bit depth limitation as Jerryno described.) – Mentalist Sep 14 '21 at 06:57

1 Answers1

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There is banding in both your pictures. I increased the contrast so you can see clearly on any display:

enter image description here

You remove banding by introducing noise, the process is called dithering:

Rendered image shows visible "line strokes" artefacts

So the denoiser removed the noise making the banding more visible. If you'd save that in 16bit and view on 12bit display using quadro graphics there would be no visible banding.

If you'd render the image without denoiser for a lot more samples to clear the noise, you'd see the same banding problem.

If you want to have smooth looking gradients on 8bit displays you need to use dithering (introduce noise). This can be noise from Cycles itself (to be perfect Maxwell produces more natural noise for example), or if you get rid of the noise with denoiser a noise introduced in postproduction through dithering.

Jaroslav Jerryno Novotny
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