Sharpening enhances the definition of edges in an image. Whether your images come from a digital camera or a scanner, most images can benefit from sharpening. The degree of sharpening needed varies depending on the quality of the digital camera or scanner. Keep in mind that sharpening cannot correct a severely blurred image.

Notes and tips about sharpening:

• Sharpen your image on a separate layer so that you can resharpen it later if you need to output it to a different medium.

• If you sharpen your image on a separate layer, set the layer’s blending mode to Luminance to avoid color shifts along edges.

• Sharpening increases image contrast. If you find that highlights or shadows are clipped after you sharpen, use the layer blending controls (if you sharpen a separate layer) to prevent sharpening in highlights and shadows. See Specify a tonal range for blending layers.

• If you need to reduce image noise, do so before sharpening so that you don’t intensify the noise.

• Sharpen your image multiple times in small amounts. Sharpen the first time to correct blur caused by capturing your image (scanning it or taking it with your digital camera). After you’ve color corrected and sized your image, sharpen it again (or a copy of it) to add the appropriate amount of sharpening for your output medium.

• If possible, judge your sharpening by outputting it to the final medium. The amount of sharpening needed varies among output media.

For greatest control use the Unsharp Mask (USM) filter or the Smart Sharpen filter to sharpen your images. Although Photoshop also has the Sharpen, Sharpen Edges, and Sharpen More filter options, these filters are automatic and do not provide controls and options.

You can sharpen your entire image or just a portion defined by a selection or mask. Because the Unsharp Mask and Smart Sharpen filters can be applied to only one layer at a time, you might need to merge layers or flatten your file to sharpen all image layers in a multilayered file.