7. The Menus / 7.7 The Filter Menu
This filter works similar to the sharpen filter and therefore is used in the same fields. However, Unsharp Masking is much more sophisticated, as it works by first creating a special mask layer to limit the sharpening only to high contrast areas. Its results are of a higher quality but the speed is slower, too.
Small filter radii - often in combination with a high intensity - are used to increase the sharpness in an image.
Big filter radii in combination with a small intensity can be used to increase the local contrast in an image. The result is similar to "clarity" known from other software.