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Hour 17. Using the Improvement Filters > Task: Applying the Unsharp Mask Filter

Task: Applying the Unsharp Mask Filter

Open an image in Elements and make whatever corrections or alterations it needs. Zoom in or out so the picture is at its full size on the screen. (This will let you see the effects of sharpening, without exaggerating them.) When you’re satisfied with everything except the sharpness, open the Unsharp Mask dialog box (Filter, Sharpen, Unsharp Mask).

Set the Amount to 500% to start with. This is the maximum, and starting here will help you see and understand what the other two variables are doing.

Set the Radius to 1 pixel, and the Threshold to 0. The picture won’t look right—it will probably look very grainy, but this is our jumping-off point.

If there is obvious grain or noise, increase the Threshold. Start with 2, and then try 5, 8, 12, and so on until the noise disappears.

Now, we’ll work with the Radius. Increase the Radius until the picture just starts to lose detail, and then back it off a bit. Figure 17.5 shows my image at this stage. (Don’t worry about the white halos around edges. We’ll lose them next.)

Figure 17.5. We’ll lose the halos in the next step.

Now, reduce the Amount until the picture looks good. You want to get rid of the white edges, but still keep the sharpening effect. You’ll probably find that the correct setting for Amount is somewhere between 100 and 250. Of course, it also depends on the amount of contrast and fuzziness in the picture you’re working on. If you’re not going to use the image onscreen (on the Web, for example) and you’re just trying to get the sharpest image you can for printing, you may want to oversharpen the image just a bit.

Finally, save the picture and print it or put it on your Web page, or do whatever you’d planned. It’s as sharp as it’s ever going to be.

Lack of sharpness in either a scanned image or a digital photo is a very common problem, and part of the reason for it is the process. The picture is saved as a series of dots. Inevitably, there are spaces between the dots, and if you have a low resolution scan or a low resolution camera (anything less than 1 megapixel), the spaces will be large enough that the software will add blur to fill them in. That’s why the pictures look fuzzy, and why adding contrast at the edges fixes it.



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