The Sharpen Palette will then display, showing 3 available adjustment selections, a) Amount, b) Radius, c) Threshold.

Amount determines the amount of sharpening you wish to apply to the image. High resolution images or images destined for print often require more sharpening than low resolution images.

Radius sets the amount of sharpening around edges of objects, the higher the setting the more edges and pixels within the image will be sharpened. Radius at low settings (between 0.5 and 1.0) is often sufficient to effectively sharpen most images. If you are trying to create a special effect in a graphics image, however, a high amount of Radius will make objects appear to "sparkle", but will look unnatural in a normal photographic image.

Threshold functions a bit different from Amount and Radius, in that the higher the setting, the less amount of sharpening occurs within the image (which is opposite from both the Amount and Radius sliders).

Theshold determines how many pixels within the image will be considered an 'edge pixel', and therefore will be sharpened, and how many will be "ruled out" and hence will not be sharpened. Using the Sharpening technique that I am about to explain to you, you will not need to use Threshold and can leave its setting set to zero.