Gamma value
                              Try to increase the Pixel Type of the composition that has the problem.
          
 
                    
                              A known example is to use a 
                     Displace
                    Move each pixel in a direction given a distortion map
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Displace
                    Move each pixel in a direction given a distortion map
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                     in Height Map mode in a HDR16 composition.
          That can be fixed if you switch the Compo in HDR32.