Absolute Beginner's Guide to Digital Photography

To sharpen your own images, open an image in Photoshop or Photoshop Elements

and choose Filter, Sharpen, Unsharp Mask. In the Unsharp Mask dialog box, you

need to adjust three settings:

■ Amount. This slider controls the strength of the sharpness mask. Amount

also controls how much the contrast between pixels is increased.

■ Radius. This slider controls distance. Radius controls how far from each pixel

the effect extends. Ugly effects are often caused when too large a radius is

chosen. For most printed images, a radius of .5 to 2 is sufficient.

■ Threshold. This slider controls sensitivity. Threshold sets a requirement on

the amount of contrast between neighboring pixels. If the contrast between

neighboring pixels is below the threshold, no sharpening will occur. The

range is 0–255. In images with skin tones, a higher threshold number is rec-

ommended to prevent unwanted skin texture.

Experimentation is an essential part of learning to use Unsharp Mask. You can

always undo your changes by choosing Edit, Undo Unsharp Mask afterward or File,

Revert to return to the original image.

Degrees of Unsharp Masking

You can easily ruin an image by abusing this powerful filter. Take the following

image, for instance (see Figure 13.2). The image was printed at 300 ppi without the

Unsharp Mask filter. The original image is basically acceptable.

CHAPTER 13 THE IMPORTANCE OF FILTERS 193

FIGURE 13.2
Image before
using Unsharp
Mask.