Sharpen effect

Sharpening increases edge contrast so details look crisper. Most tools compare each pixel with a blurred version of the image and boost the difference, which is the idea behind the classic unsharp mask.

Amount sets how strong the effect is, and Radius sets how wide the edges it affects are. A small radius sharpens fine detail such as hair and texture; a larger radius adds punch to bigger shapes but risks light halos around edges.