User Guide

CHAPTER 6
128
Making Color and Tonal Adjustments
Step 6: Sharpen the image
Unsharp masking, or USM, is a traditional film
compositing technique used to sharpen edges in
an image. The Unsharp Mask filter corrects
blurring introduced during photographing,
scanning, resampling, or printing. It is useful for
images intended both for print and online.
Numbers represent Unsharp Mask amount, Radius, and
Threshold.
The Unsharp Mask filter locates pixels that differ
from surrounding pixels by the threshold you
specify and increases the pixels’ contrast by the
amount you specify. In addition, you specify the
radius of the region to which each pixel is
compared.
The effects of the Unsharp Mask filter are far more
pronounced on-screen than in high-resolution
output. If your final destination is print, exper-
iment to determine what dialog box settings work
best for your image.
To sharpen an image using the Unsharp Mask filter:
1 Choose Filter > Sharpen > Unsharp Mask.
2 Sharpen the image:
• For Amount, drag the slider or enter a value to
determine how much to increase the contrast of
pixels. For high-resolution printed images, an
amount between 150% and 200% is recom-
mended.
• For Radius, drag the slider or enter a value to
determine the number of pixels surrounding the
edge pixels that affects the sharpening. For high-
resolution images, a Radius between 1 and 2 is
recommended.
A lower value sharpens only the edge pixels,
whereas a higher value sharpens a wider band of
pixels. This effect is much less noticeable in print
than on-screen, because a 2-pixel radius represents
a smaller area in a high-resolution printed image.
• For Threshold, drag the slider or enter a value to
determine how different the sharpened pixels
must be from the surrounding area before they are
considered edge pixels and sharpened by the filter.
To avoid introducing noise (in images with flesh-
tones, for example), experiment with Threshold
values between 2 and 20. The default Threshold
value (0) sharpens all pixels in the image.
300,1,15200,2,0
200,1,00,0,0