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Color Plate 37-1.
Use the sliders to set the Amount, Radius, and Threshold.
The Amount sets how much the edges in the image are enhanced and defined (that is, sharpened). The higher the setting, the more sharpening.
The Radius sets how contrast is increased from the edges. Higher settings make thicker edges.
The Threshold sets how precisely the edges are recognized. Lower settings sharpen more pixels. Higher settings sharpen fewer pixels.
Experiment especially with the Amount and Radius settings. Find out where the settings go off the charts and create an undesired effect for you. Take a look at Figure 37-3, which shows the image from Figure 37-1 sharpened with various settings.
The name seems like a contradiction, doesn’t it? The best sharpener in Photoshop is termed unsharp. Hmph. The term unsharp mask actually comes from photography, where a negative and a faint positive created by using a special film (called masking film) are sandwiched together to increase contrast and sharpness. The faint positive created by using masking film is called an unsharp mask. I guess some of the programmers at Adobe are real photography buffs.
Here’s how to use the Unsharp Mask filter:
Open the image that you want to sharpen.For this example, I’m using the wagon wheel pasta shown in Figure 37-1. As you can see, the photograph is distinctly blurry.
Figure 37-1: This blurry pasta is going to become clearer.
Choose Filter>Sharpen>Unsharp Mask.The Unsharp Mask dialog box opens, as shown in Figure 37-2.
Figure 37-2: The Unsharp Mask dialog box is your key to sharper images.
Figure 37-3: Different settings create more contrast at the edges.
Click OK when you finish adjusting the sliders to apply the sharpening to the image.After applying the Unsharp Mask, you can always apply other filters to accentuate the edges. Figure 37-4 shows two filters applied to the pasta wheels after extreme sharpening with the Amount set at 500% and the Radius set at 5. First, the Plastic Wrap filter was applied (top). Then, the Glowing Edges filter was applied (bottom).
Figure 37-4: Applying filters after sharpening can increase the effects of the filters.
| Tip | You can also apply the Unsharp Mask to individual channels. Experiment with this and see how sharpened channels can create colored edge glows. (For that matter, you can apply any filter to individual channels.) Take a look at Technique 52 to find out more about working with channels. Turn to Color Plate 37-1 to see these channel effects. |
| Tip | Sometimes applying the Unsharp Mask several times with lower settings works better than applying the filter once with higher settings. |
