The Compare function can be used to compare pixel differences between one separation and another separation. File sizes (in pixels) must be identical to be compared.
You can also compare one set of separations to another set, provided that you compare the same number of separations.
First Open the separation (or set of separations) you wish to compare.
The choose Edit > Compare... or click the Compare icon 
in the Toolbar.
The original file name will be identified in Blue under the Inventory > Separations list, and the compared file name will be identified in Red.
The display shows all pixels that are identical in each file as Gray, pixels unique to the original file as Blue and pixels unique to the compared file as Red.
