Almost all digital images need some degree of sharpening to bring out detail in the subject.
Sharpening filters bring out detail by increasing the contrast of pixels next to one another. More advanced image editing programs offer several options such as Sharpen, Sharpen More, Sharpen Edges, Smart Sharpen and Unsharp Mask (USM). Unsharp Mask gives you a lot of control over how an image is sharpened. Even basic editing programs, such as Picasa, offer a Sharpen feature, though it usually sharpens all parts of an image equally, giving you no control.
A photo may benefit from selective sharpening. You select an area with a programs selection tool and only sharpen the selected area. The important thing is not sharpen an image too much.
The Unsharp Mask filter corrects the softness often visible in digital photos. It also corrects blurring that occurs when an image is reduced in size.
This tutorial is illustrated using Photoshop. Click image for a larger view of the Unsharp Mask options.
Begin by opening an image then selecting the menu and sub menus Filter > Sharpen > Unsharp Mask.
Check Preview so you can watch changes take place the sliders are adjusted.
The Amount Slider increases the contrast of image pixels.
The Radius Slider determines the number of pixels near edge pixels that are influenced by the amount of sharpening.
The Threshold slider is used to prevent introducing noise.
The degree of sharpness depends on the settings used. Programs such as Photoshop also let you “fade” the effect to reduce the overall sharpness. Experiment a bit until you are satisfied with the degree of sharpening.
The results of using Unsharp Mask filter are more pronounced when preparing an image for online viewing. You may need to use different settings when preparing an image for print.