31 Replies Latest reply: Mar 23, 2011 9:03 PM by Noel Carboni RSS

    Funky Banding Seen in PS CS5 Color Management with Some OpenGL Modes

    Noel Carboni Community Member

      While experimenting with gradients and large gamut color spaces in response to another post, I came across a peculiarity with displaying image documents in Photoshop CS5 that are using ProPhoto RGB when OpenGL is enabled.

       

      The test is a simple radial gradient from black to gray using 16 bits/channel and the ProPhoto RGB document profile.  In my test setup, I am using the standard Windows-supplied sRGB profile for my monitor, and the video card is an ATI Radeon HD 4670 running Catalyst 11.1 drivers.  The following are screen grabs using the same technique and software in all cases.

       

      Exhibit A follows:  This is the display with OpenGL Disabled or Enabled in Basic mode.  Note the perfectly smooth gradient.

       

      ProPhotoRGBShowingNoBanding.png

       

       

      Test 2 (below):  Same document as above, OpenGL enabled in Normal and Advanced modes). Note the slightly colored posterization / bands in the display of the gradient.

       

      ProPhotoRGBShowingColorBanding.png

       

       

      This is not a limitation of my video card's OpenGL implementation, because on this very same system one of my own applications, using 16 bit color management and OpenGL (GL_RGBA16 format specifically) displays a smooth, clean gradient.

       

      Here is the Photoshop file from which I generated the above displays.  I'd be curious to hear whether you see something like the first or second image when you open it in Photoshop CS5.

       

      http://Noel.ProDigitalSoftware.com/temp/TestGradient.zip

       

      -Noel