By printing each color separation of a file on a clear overlay material each color can be proofed separately or superimposed on each other to proof the entire page. Overlay proofs
are created from the film separations that places each ink color on a separate clear acetate sheet or film material then stacks them together in alignment (registered) over white paper or other substrate.
Cromacheck and Color Key overlay proofs are two brands of overlay proofing systems.
Also Known As: Color Key | Cromacheck | progressives
Use overlay proofs to check registration, trapping, and color breaks, identify density problems and pixelation of bitmaps. Can be used for process and spot color jobs. Overlay proofs are less reliable than laminate proofs for checking color.