Applying the Unsharp Mask filter
In order to do its job of sharpening, the Unsharp Mask filter increases the contrast between adjacent pixels. To control the level of contrast, you will choose settings for three variables: Amount, Radius, and Threshold.
To apply the Unsharp Mask filter:
- Choose a zoom level of 50–100% for your image.
- Duplicate an image layer (Ctrl-J/Cmd-J),A then right-click the duplicate layer and choose Convert to Smart Object.
- With the Smart Object layer selected, choose Filter > Sharpen > Unsharp Mask.
- In the dialog, choose an Amount percentage to control how much the contrast will be increased.B For some recommended settings, see the sidebar on this page.
- The Radius setting controls how many neighboring pixels around high-contrast edges the filter affects. When setting a value, consider the pixel count of the image and its subject matter. The higher the pixel count, the higher the Radius value needed.C For a low-contrast image that contains large, simple objects and smooth transitions, try a high Radius of 2; for an intricate, high-contrast image that contains many sharp transitions, try a lower Radius of around 1.
- Choose a Threshold value to establish how different in value an area of pixels must be from an adjacent area for it to be affected by the filter.A Start with a Threshold value of 0 (to sharpen the entire image), then increase it gradually. At a Threshold of 5–10, high-contrast areas will be sharpened and areas of lesser contrast will be sharpened much less. When increasing the Threshold, you can also increase the Amount and Radius to sharpen edges. A proper Threshold setting will prevent the filter from oversharpening low-contrast areas.
- Click OK.B To adjust the filter settings at any time, double-click the Unsharp Mask listing on the Layers panel.
A This original 300 ppi image is slightly blurry.
B A high Amount value and a low Radius value for the Unsharp Mask filter barely sharpened the image.
C A high Radius value of 4.0, on the other hand, produced ugly halos around the numerals on the ruler and on the blue lines of the graph paper.
A At a high Threshold value of 12, the Unsharp Mask filter sharpened only the high-contrast edges. The lower-contrast (light blue) lines on the graph paper remained blurry.
B A low Threshold value of 0–1 worked better for this image because it contains a lot of flat surfaces, hard edges, and fine lines.