This chapter will explain the use of these filters. Keep
in mind while reading that filters only work on layers
that contain pixels. In other words, make sure the
correct layer is selected or the filter won’t do any-
thing. In particular, filters do not work on adjust-
ment layers, so make sure the actual image is
selected rather than an adjustment layer.Sharpening Prints
Digital sharpening accentuates the existing details
in an image. It increases the perception of sharp-
ness in a print, but it cannot create detail where
there is none. Most scanned images need some
sharpening because the scanning process can blur fine details. The most helpful
sharpening technique is called unsharp masking(see Figure 13.1).192 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
Adjustment layers are
explained in Chapter 16,
“The Importance of Layers and
Masks.”FIGURE 13.1
Controlling an
unsharp mask.Unsharp Mask is a filter that works by comparing neighboring pixels and increasing
the contrast between them. It makes light pixels lighter and dark pixels darker, so
that the contrast of fine details is enhanced. In areas of smooth, flat tone where there
is no difference between neighboring pixels, the filter doesn’t change the pixels.
Unsharp masking gets its paradoxical name from a rarely used darkroom procedure
that creates an illusion of sharpness in prints. An out-of-focus (“unsharp”), low-con-
trast, positive image (“mask”) is made by contact printing from a negative. The two
films are sandwiched together and printed with higher contrast.