Editing Unsharp masking (section)

{{Short description|Image sharpening technique}}
[[File:Usm-unsharp-mask.png|thumb|Unsharp masking applied to lower part of image]]
'''Unsharp masking''' ('''USM''') is an [[image sharpening]] technique, first implemented in [[Analog photography|darkroom photography]], but now commonly used in [[digital image processing]] software. Its name derives from the fact that the technique uses a [[Gaussian blur|blurred]], or "unsharp", negative image to create a [[Mask (computing)|mask]] of the original image. The unsharp mask is then combined with the original positive image, creating an image that is less blurry than the original. The resulting image, although clearer, may be a less accurate representation of the image's subject. 

In the context of [[signal processing]], an unsharp mask is generally a [[linear filter|linear]] or [[nonlinear filter|nonlinear]] filter that amplifies the high-frequency components of a signal.