
An "unsharp mask" is actually used to create a sharper image, contrary to what its name might lead you to believe. Sharpening can help emphasize texture and detail, and is critical when post-processing most digital images. Unsharp masks are probably the most common way to create a sharper image, and can be performed with nearly any image editing software (such as Photoshop). An unsharp mask cannot create additional detail, but it can greatly enhance the appearance of detail by increasing small-scale acutance.
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