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This chapter is from the book


The Sharpen slider is definitely not a panacea—it can't restore details that weren't part of a picture to begin with—but it can create the illusion of a sharper image. It's more of that Photoshop Elements magic, and it's based on some pretty heavy-duty math, combined with an old-time darkroom technique.

How Sharpening Works

Let's start by reviewing the darkroom trick. It's called unsharp masking, and it goes something like this:

  1. Put the negative of your blurry picture on top of a glass plate, with unexposed film under the glass.
  2. Make a copy of the negative on the new film, which gives you an inverted version of the negative—a positive. In addition to being inverted, the new copy is slightly distorted because the light that produced it had to pass through the glass plate.
  3. So now you make a very short-exposure print of the positive. Then on the same paper you print the original negative.

What you get is an image with its edges highlighted because of the slight difference between the negative and the positive. And highlighted edges look sharper and more detailed.

Now let's translate that into mathematical terms to see what Photoshop Elements does. On second thought, let's not. Math is what computers do best, and we don't need to know how it works to use unsharp masking with Photoshop Elements. All we need to do is use the Sharpen Quick Fix.

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