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You can revive lost details by applying a filter that sharpens the image by heightening the difference between adjacent pixels. This increased intensity of color and brightness makes everything stand out, as shown in Figure 1, where some of the image has been sharpened and the rest was left as it was.
You can use the Sharpen filters that come with all image editing applications or use the Sharpen tool that you find in the toolbox of just about any image editing program. To use the filter, you need to select the area that you want to sharpen and then apply the filter. To use the tool, you only need to make the standard brush-related adjustments (such as the size of the brush and the degree of sharpening that it applies).
Figure 1: Sharpening enhances the contrast between adjacent pixels.
If you want to sharpen the entire image, use a filter to do the sharpening. If your software doesn't have filters, check for a Sharpen command or reasonable facsimile thereof — any command that performs an automatic, all-over sharpening works fine. The other benefit of this process is that you can do it simply in most image editors. Corel PhotoPaint, Paint Shop Pro, and Adobe's image editors, for example, all have a simple Sharpen command that you can apply directly, along with more sophisticated versions if you need more control.
If you want to sharpen an area, you can also use the filter or automatic sharpening command, but you have to make a selection first, directing the software to the spot that you want to sharpen. You can repeat the process to sharpen two or more unconnected areas. Or if your software supports selections that don't touch, select all the areas that you want to sharpen and then apply the filter or related command.
When you need to sharpen a little here, a little there, a bit more here, and a whole lot there, you can use the Sharpen tool that some image editors provide for "painting" sharpness. It works like a painting tool in that you click and/or drag your mouse over the image to apply the sharpening effect. You can repeat your mouse movements in the same spot if you want more of a sharpening effect in one place than in another. You can dictate the size of the sharpened area by adjusting your brush size, and you can control the intensity of the sharpening by adjusting the strength setting.
To use a Sharpen tool, follow these steps:
1. Turn on the Sharpen tool by selecting it from your image editor's toolbox or menu.
2. Set your brush size so that you can control how big an area the tool sharpens with each click or drag of the mouse.
3. Set the strength for your sharpening effect.
A good default value is 50%, but you can raise or lower that level as you need by dragging the slider or other control.
4. Begin sharpening by clicking or dragging over the area that you want to sharpen.
Clicking sharpens an area the size of your brush tip, and dragging lets you sharpen in a freeform area, following an edge or working within a desired region of the image.
 | Be careful not to sharpen too much. Too much sharpening results in bizarre-looking bright pixels that end up hiding details because the individual pixels stand out too much. Sharpening can also increase your file size. |
 | To keep the sharpening results as subtle as possible, avoid using a very small brush size (10 pixels or fewer) if you're sharpening an area that's more than 20 pixels wide and/or tall. Why? Because you can see your brush strokes as you apply the sharpening with such a small brush size. But if you want to sharpen a very small spot, which obviously calls for a very small brush, you can select the area first, which helps control your effects by restricting them to the selected area. |
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