The Unsharp Mask filter reproduces a traditional film technique used to sharpen edges in an image. The Unsharp Mask filter corrects blur introduced during photographing, scanning, resampling, or printing. It is useful for images intended for both print and online viewing.
Unsharp Mask locates pixels that differ from surrounding pixels by the threshold you specify and increases the pixels’ contrast by the amount you specify. For neighboring pixels within the specified radius, the lighter pixels get lighter, and the darker pixels get darker.
The effects of the Unsharp Mask filter are far more pronounced on‑screen than in high-resolution printed output. If your final destination is printed output, experiment to determine what settings work best for your image.