GIMP's filters include the "Unsharp Mask" option.
The GNU Image Manipulation Program is a free editor that can enhance your digital images. GIMP features the "Unsharp Mask" filter that sharpens slightly blurry images. Three options adjust the level of sharpening: "Radius", "Amount" and "Threshold." The "Radius" affects the pixels surrounding edges. The "Amount" affects the strength or intensity of the sharpening filter. The "Threshold" applies a minimum difference or threshold in pixel values where the sharpening occurs.
Instructions
1. Open the GIMP program. A blank image window appears.
2. Click the "File" menu. A list of commands appears.
3. Click "Open." The "Open Image" dialog window appears
4. Click to open the image file's folder location.
5. Double-click the image file. You can also just click the file once and then click the "Open" button at the bottom of the dialog window. The image appears in the image window.
6. Click the "Filters" menu. A list of filters appears.
7. Point the cursor over the "Enhance" option. A list appears to the right.
8. Click the "Unsharp Mask" option. The "Unsharp Mask" dialog box opens. You will see a "Preview" box and three slider options.
9. Click to select the check box for "Preview."
10. Click and drag the slider button for each of the three options: "Radius," "Amount" and "Threshold." "Radius" has values 0.1 to 120. For a higher resolution image, try setting a higher radius. "Amount" has values 0 to 10. Selecting a higher value will distort colors. "Threshold" has values 0 to 255. Higher threshold values allow you to keep areas with smooth tones from developing unwanted edges.
11. Preview the effect of each option in the "Preview" box. Click and drag the horizontal and vertical scroll buttons to view the effects on other areas of the image.
12. Click "OK."
Tags: Unsharp Mask, appears Click, Amount Threshold, Amount Threshold Radius, Click drag, dialog window
