UMAX Technologies PowerColor, User Manual, Page: 111 / 127

Chapter 6: Unsharp Masking 6-3
Various fields in the USM window determine how the tonal regions are handled.
These are defined as follows:
• Sharpen: governs the amount of sharpening applied to the selected tonal
region. To define a desired sharpening value for a region, click on the
region’s bar in the chart (it turns red) and enter the value in this field.
• Threshold: refers to the minimum difference between dark and light areas
that must exist before unsharp masking is applied. The lower the threshold
value, the smaller the difference between the pixel values needs to be to
apply USM. As you raise or lower the value in this field, the active bar is
shifted up or down in the chart to reflect the higher or lower starting point
for USM. Areas below the threshold are smoothed (see below); areas above it
are sharpened.
• Smooth: evens out differences between tonal regions in an image. This
option is helpful, for example, in reducing the effect of film grain (typically
in the shadows or three-quarter tones) when an image is magnified. A high-
er Smooth value helps to diminish the film’s graininess.
Smoothing is represented in the Region Control chart by the lighter colored
bar to the right of each dark bar. As you increase the Smooth value, the
lighter bar gets longer, graphically representing the smoothing effect
between two adjacent regions.
Note: Only those areas below the threshold are
smoothed.