Standards Based Development

Sharpening an Unsharp Mask

Unsharp masks are actually used to sharpen images.

Open Photoshop: Filter > Sharpen > Unsharp Mask.

Unsharp Mask has three settings:

Amount: Controls the magnitude of each overshoot, typically a "%"; Another way to put it: this can be thought of as how much contrast is added at the edges.
Radius: Controls the amount of blur on the original (this creates the mask); affects the size of the edges behind enhanced, a smaller radius enhances smaller-scale detail.
Threshold: Sets the minimum brightness change that will be sharpened; equivalent to clipping off the darkest non-black pixel levels in the unsharp mask. Threshold setting can sharpen pronounced edges while leaving subtle edges untouched: such a technique is especially useful to avoid amplifying noise, or to sharpen an eye lash without roughening skin texture.