Adobe Photoshop CS3 - Manual (Page 216)

PHOTOSHOP CS3
User Guide
209
Radius Controls the size of the area around each pixel that is used to determine whether a pixel is in the shadows or
highlights. Moving the slider to the left specifies a smaller area, and moving it to the right specifies a larger area.
5 Click OK.
Sharpen using Unsharp Mask
The Unsharp Mask sharpens an image by increasing contrast along the edges in an image. The Unsharp Mask does
not detect edges in an image. Instead, it locates pixels that differ in value from surrounding pixels by the threshold
you specify. It then increases the contrast of neighboring pixels by the amount you specify. So, for neighboring pixels
the lighter pixels get lighter and the darker pixels get darker.
In addition, you specify the radius of the region to which each pixel is compared. The greater the radius, the larger
the edge effects.
Original image, and Unsharp Mask applied
The degree of sharpening applied to an image is often a matter of personal choice. However, oversharpening an
image produces a halo effect around the edges.
Oversharpening an image produces a halo effect around the edges.
The effects of the Unsharp Mask filter are more pronounced on-screen than in high-resolution output. If your final
destination is print, experiment to determine what settings work best for your image.
1 (Optional) If your image is multilayered, select the layer containing the image you want to sharpen. You can apply
Unsharp Mask to only one layer at a time, even if layers are linked or grouped. You can merge the layers before
applying the Unsharp Mask filter.
2 Choose Filter > Sharpen > Unsharp Mask. Make sure the Preview option is selected.
Click the image in the preview window and hold down the mouse to see how the image looks without the sharpening.
Drag in the preview window to see different parts of the image, and click + or – to zoom in or out.
Although there is a preview window in the Unsharp Mask dialog box, it’s best to move the dialog box so you can
preview the effects of the filter in the document window.