- Choose Filter, Sharpen, Unsharp Mask. Check the Preview check box. A check
in this box lets you preview the sharpening effect across the monitor screen.
Set the image magnification at 100%. Clicking Preview on and off repeatedly
lets you compare the sharpened and unsharpened images. - Determine the radius first. For a printed image, divide the pixels per inch in
the print by 200. For example, for 180 pixels per inch, divide 180 by 200. The
radius is therefore .9. If you are printing at 300 pixels per inch, divide 300 by
200; your radius will be 1.5 (see Figure 13.6). If you are preparing an image
for display on the Internet or in multimedia, simply use a radius of .5.
196 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
FIGURE 13.6
Determining
the radius in
the Unsharp
Mask filter.- Determine the best amount. Temporarily set
the threshold to 5 and adjust the amount. Try
amounts between 50 and 300 percent to see
what works best. There is no magic number
here—each image benefits from different
amounts, depending on the image’s sharp-
ness, the subject matter, and the scan’s
graininess. - Finally, experiment with the threshold. If the
image is grainy or if skin tones are promi-
nent, you will need to use a higher value for
the threshold. Raising the threshold
decreases the sharpening effect, so if you sig-
nificantly raise the threshold, you might
need to compensate by increasing the
amount.
Pixels per inch is not
the same as the printer’s
dots per inch. These two terms
measure different things. Ignore
the printer’s dots per inch and cal-
culate the radius using pixels per
inch.