In color separation photography, a somewhat blurry, low contrast photographic negative produced from a transparency and placed on top of the transparency (as a mask) when exposing the color separation negatives. The light passing through the mask is altered, resulting in a color correction that compensates for the hue errors of process inks. An added benefit of the unsharp mask is that the edges of the images on the transparency are enhanced (or exaggerated) which produces greater detail on the color separation negatives. This process is called unsharp masking.
Digital image-processing programs and scanners also employ types of unsharp masks to sharpen the edges of images. See Unsharp Masking.