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e ch n
e ch n
Inspiring
November 22, 2023
Question

Pattern and rainbow on shadow?

  • November 22, 2023
  • 1 reply
  • 418 views

Hello. Can someone help me with this?

 

Why does this pattern appear in the shadow?

Plus, it has like a rainbow appearance.

 

Can those anomalies be avoided so the shadow can be seen without those effects, and how should it be done?

 

Thanks! 

 

    This topic has been closed for replies.

    1 reply

    davescm
    Community Expert
    davescmCommunity Expert
    Community Expert
    November 22, 2023

    First try working in 16 bits/channel rather than 8 bits/channel. If you need to convert to 8 bit at some point, add a little noise. Very little is required to hide such artifacts.

     

    If that does not impact the issue, can you confirm what brushes you are using and your system details (in particular the GPU)

     

     

    Note - You may still see such artifacts when working with smooth gradients in 16 bits /channel then they are on your display - not the image. Many displays, with the exception of some higher end 10 bit/channel monitors, display in 8 bits/channel and some use just 6 bits+dither.

     

    Dave

      e ch n
      e ch nAuthor
      Inspiring
      November 26, 2023

      Hello, davescm.

       

      I apologize for responding days later, I have several cases open and I attend to them as the conditions and circumstances arise.

       

      Yes, certainly exporting the image to 16 bit helped. Really, thank you very much for responding.

       

      I also applied the noise that appears by default when opening the window of that tool, I left it like this because you suggested that it be little, although I honestly did not perceive any modification, maybe I should apply more noise... I don't know. I have attached a screenshot of the noise applied.

       

      Here are the images according to the export processes. (Although apparently, before posting this message, the images cannot be shown in real size... Which makes it difficult to appreciate the details.)

       

      It draws my attention that you comment that if I keep seeing this anomaly, it would be my monitor... I attached a screenshot of the general configuration of the screen, let's see if that helps to know if it is indeed the monitor.

       

      Again, thank you very much davescm.

       

       

      Original 8-bit JPG with the plot and the rainbow.

       

      16-Bits- with Noise.

       

      Applied noise

       

      Export settings

       

       

      Mac settings

      davescm
      Community Expert
      davescmCommunity Expert
      Community Expert
      November 26, 2023

      Hi

      I can't really judge the 16 bit version as, as soon as you export it as a jpeg to show it here, it becomes 8 bit (jpeg only supports 8 bits/channel)

      On the noise, I tend to use monochromatic noise and it only needs to be applied to the shadow layer. 1 or 2% may be enough to hide the banding.

       

      Unfortunately I don't use a Mac so I'm not able to comment on whether your display is 8 bit or 10 bit. There is a test for it though.

      First in Photoshop Preferences > Performance > Graphics Processor > Advanced Settings make sure 30 bit display is enabled.

      On windows - you also need to ensure your GPU driver is set up to work in 10bits/channel (I am not sure on teh Mac)

      Next open a 16 bit/channel RGB document and create a gradient, using the gradient tool across the document running from black 0,0,0 to dark grey 40,40,40. with Dither unchecked in the options bar.

      Is the gradient perfectly smooth or do you see any banding (distinct steps or coloured bands). If smooth then your display is likely working in 10 bits/channel. If you do see bands it is likely to be working in 8 bit.

       

       

      Dave

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