Unsharp Mask in Photoshop

Sharpening digital images is crucial step in getting your photos ready for print, and can also greatly improve the quality of photos for online presentation.

"Unsharp Mask" is a filter found in Photoshop and other graphic programs. In Photoshop, you can find Unsharp Mask in: Filters > Sharpen > Unsharp Mask.

There are 3 settings under this filter:

Amount
Defines how much sharpening is to be applied to a photo...increasing this setting increases the contrast along edges, making darker areas darker; lighter areas lighter. An amount setting of 75-125 is a good starting point to begin experimentation.

Radius
Is the size of the area around pixels that will be affected. Increase this setting as resolution/file size increases. So, for screen resolution (online presentation) a radius of around .5 usually works. For most photos headed for the printer, a radius of 1.2 - 1.5 is recommended. For photos without much detail, increasing this setting to around 3 can improve upon the photo greatly.

Threshold
Defines how much of the photographs data/detail will be used to apply change. At 0, the filter will affect everything...at higher settings the less detailed the sharpening will be. A threshold of 3-4 is a good starting point.

For portraits, an increased setting of around 6 would be best (if you don't want those pores and pimples being sharpened for you viewing pleasure.)

So, settings of

125 - 1.5 - 3 (for print)
100 - .5 - 3 (for web/screen)

are basic starting points to start tweaking from.

Important Notes:

When sharpening for print, the on-screen preview of the photo will usually look over-sharpened; even though when printed the amount seems just right. Tests-runs, experience over time, and talking to your printer will help you make sharpening decisions for print.

The Unsharp Mask is not for fixing blurry images, only to bring out detail in an already focused image.

Sharpening should be the last, or one of last edits you perform on your image.

Be careful when sharpening photographs with flesh, over-sharpened skin can look icky.

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