Unsharp Mask

Unsharp masking is a traditional technique that has been used in the printing industry for many years. It is probably your best bet for precision sharpening. It corrects blurring in an original image or scan, as well as any blurring that occurs during the resampling and printing process. The Unsharp Mask filter works by locating every two adjacent pixels with a difference in brightness values that you have specified, and increasing their contrast by an amount that you specify. It gives you real control of the sharpness of an image.

Set the level of sharpening you need in the Unsharp Mask dialog box shown in Figure 15.5; the dialog box appears when you select the filter. The Radius control sets the number of surrounding pixels to which the sharpening effect is applied. I suggest that you keep the radius fairly low—around 2.0. The Threshold setting controls how different the pixels must be to be sharpened. The lower the setting, the more similar the pixels can be and still be affected by the filter. The higher the setting, the greater Photoshop's tolerance of differences will be. (Of course, as always, feel free to go wild and try all the settings. That's the best way to learn.) Be sure that you check the Preview box so that you can see the effect of your changes.

Many Photoshop experts recommend applying the Unsharp Mask filter to every image that you process, whether it's going to be printed or used on the Web. (I personally don't like to say always or never because there can be exceptions to any rule.) You should probably try it on every image, to see whether you like the effect.

Unsharp Mask

' Cancel 0 Preview

Threshold: [4 j levels A-

Threshold: [4 j levels A-

FIGURE 15.5

The preview area lets you see the effect your settings have.

0 0

Post a comment