Behind the Unsharp Mask: The Secret World of Sharpening

Proper sharpening is a bit like black magic. We can’t really sharpen an image any more than it already is. If it wasn’t sharp when captured, there’s nowhere the information needed can come from later on. What we can do is create the illusion of sharpness by exaggerating contrast along edges in the image. This added contrast makes the edges stand out more, making them appear sharper.