Join Deke McClelland for an in-depth discussion in this video The mechanics of sharpening, part of Photoshop CS4: Sharpening Images New Features.
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In this exercise, we are going to take a little tour of the mechanics of Sharpening, which probably sounds hideously dull, but it's actually really great, because you are going to see how sharpening is ultimately just a little parlor trick that makes us think we're seeing more sharply focused details. And we'll also see how it compares to other parlor tricks: Height and Contrast, jagged edges, stuff like that. I'm working inside of an image called 'Sharp shapes.psd,' and it's a layered image. So, if you were to bring up the layers palette, you could tour through those layers if you wanted to.
Not really necessary, but I say that because I'm going to be touring you through Layer Comps, which are different layered states of an image. And we have got this thick dark serpentine line here, with a bunch of white circle set inside of it or light circles I should say. It's set against a light background. And then we have a Texture Pattern at work throughout everything. And that will give us a sense for where the sharpening is occurring, because when Photoshop sharpens an image, it's elevating the degree of contrast around edges. And edges are areas of rapid luminance variation.
That is, we go from light to dark very suddenly. Like this thing right here is an edge. And the perimeters of the circles, those are edges as well. And even these little bumps have edges associated with them. So the more contrast that's going on at that edge, the bigger the edge is, the bigger the precipice. And Photoshop's job is to increase that edge to make it even more of a cliff, as we'll see. All right, so I am going to go ahead and bring up the Layer Comps palette, I'll go to the Window menu and choose Layer Comps.
And as I say, Layer Comps, they allow you to save layered states inside of the image. So in our case, we are just touring the layers that I have setup in advance for you. So here's the standard version of the image. Let's go ahead and actually zoom in, so that we're really close to the image. Again 200%, so that these details survive the downsampling inherent in our video process. And I am going to switch from Standard to Sharpened, and these are the sharpened edges. Now you can sharpen an image to any degree you want to. You have all kinds of control over the sharpening process, so I don't want you to think, "This is this image sharpened." "This the only way it could be sharpened." It could to be sharpened in any number of ways. But no matter how we were to sharpen it, we would get this kind of effect where we would go from having - notice this - we have a dark edge set against the light background, if you will.
It doesn't really matter who is the background and who is the foreground, but that's what we've got. And as soon as I sharpen, I go ahead and trace an even darker halo on the dark side and a lighter halo on the light side. So we have halos around everything at this point, and they're always exaggerating the information that was already there, the luminance that it was already there are. So dark details, dark edges tend to go nearly black when we have really steep edges like this. And they go nearly white on the light side.
Now we are also elevating the degree of contrasts associated with this texture pattern here. And it's all in the name of attracting the eye's attention. So, our eyes respond to areas of rapid contrasts, and the more rapid that area of contrast, the more that seems like a tactile detail. The more our eyes read that detail as being sharply focused. Even to the point of painfully sharply focused. And that's kind of what we are looking for here. We want some nice, sharp details, where we want sharpness inside of our images.
All right, so that's the sharpened version. And I was saying, we were basically elevating contrasts throughout the image, but we are not doing a general contrast enhancement. This is what a general contrast enhancement looks like. So we go from the standard image, which has a fair amount of amount of contrast associated with it in the first place, and then we enhance that contrast like so. So the dark areas become darker, the light areas become lighter. That has nothing to do with the edges though. It's not favoring the edges at all. It's simply increasing the contrast across the board.
That does not produce the effect of height and contrast. This does. When we start to attack the edges, that's when we get sharpness. Now, you'll sometimes hear folks refer to these sharp edges as 'jagged' and I want to clarify, they aren't jagged. This right here is jagged. These are jagged transitions, and I'll go ahead and zoom in and so you can really see how jagged they are. We have all the stair stepping occurring there. That also is not read by our eyes as being sharp. That is rather read by our eyes as being bad detail inside of a pixel-based image.
I mean that's not going to get us anywhere. Whereas Sharpening looks like this. We have a high degree of contrast. We do have some stair stepping, but we've also got some natural anti-aliasing built into that so that our edges remain nice and organic. So we have what ultimately appear to be naturally focused photographs. So that gives you a sense of how Sharpening works. In the next exercise, we are going to see how Sharpening affects more gradually transitioning edges.