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3.8. Sharpen

3.8.1. Overview

Most of digitized images need correction of sharpness. This is due to digitizing process that must chop a color continuum up in points with slightly different colors: elements thinner than sampling frequency will be averaged into an uniform color. So sharp borders are rendered a little blurred. The same phenomenon appears when printing color dots on paper.

The Sharpen filter accentuates edges but also any noise or blemish and it may create noise in graduated color areas like the sky or a water surface. It competes with the Unsharp Mask filter, which is more sophisticated and renders more natural results.

Figure 16.31.  Applying example for the Sharpen filter

Applying example for the Sharpen filter

Original image

Applying example for the Sharpen filter

Filter “Sharpen” applied

3.8.2. Activate the filter

You can find this filter through FiltersEnhanceSharpen.

3.8.3. Options

Figure 16.32. “Sharpen” filter options

Sharpen filter options


Parameter setting results are interactively displayed in preview. Scroll bars allow you to move around the image.


The slider and input boxes allow you to set sharpness (1-99) and you can judge result in preview. By increasing sharpness, you may increase image blemishes and also create noise in graduated color areas.

  Published under the terms of the GNU General Public License Design by Interspire