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Photoshop CS4: Sharpening Images New Features

Amount and Radius


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Photoshop CS4: Sharpening Images New Features

with Deke McClelland

Video: Amount and Radius

Photoshop provides several different filters with which you can sharpen an image. You've got Unsharp Mask. You've got Smart Sharpen. You can use the High Pass filter. You can use Emboss. You can even use Gaussian Blur. Most of those filters offer an Amount value, and every one of them offers something analogous to a Radius setting. And we are going to be evaluating how Amount and Radius work in this exercise. I'm still working inside this serpentine diagram here, sharpshapes.psd, found inside the 01_how_it_works folder.

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Photoshop CS4: Sharpening Images New Features
58m 40s Intermediate Sep 25, 2009

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Photoshop CS4 New Features: Sharpening Images explores the changes to CS4's image-sharpening tools. As a companion to Deke McClelland's Photoshop CS3 Sharpening Images, this short course teaches the new features for sharpening in CS4, focusing on the OpenGL support. OpenGL allows the user to preview an image at the size it will print, rather than waiting on output. For more information on sharpening after this course, continue with Photoshop CS3 Sharpening Images. Exercise files accompany this course.

Subjects:
Design Photography Sharpening
Software:
Photoshop
Author:
Deke McClelland

Amount and Radius

Photoshop provides several different filters with which you can sharpen an image. You've got Unsharp Mask. You've got Smart Sharpen. You can use the High Pass filter. You can use Emboss. You can even use Gaussian Blur. Most of those filters offer an Amount value, and every one of them offers something analogous to a Radius setting. And we are going to be evaluating how Amount and Radius work in this exercise. I'm still working inside this serpentine diagram here, sharpshapes.psd, found inside the 01_how_it_works folder.

And in case you are worried that we are going to be spending the entire series inside boring diagram files, perish the thought. We are going to see some beautiful photography, over the course of this series, so stay tuned for that. Most of our work is going to be done inside of photographs. I've switched to the first Layer Comp, Standard, just to reset the image. And I am going to switch from the Layer Comps palette to the Layers palette right here. And in fact, I am going to go ahead and expand my palette, so that I can see the Layers palette and the image at the same time here. And notice that in addition to this group of layers called 'the ingredients,' which is what we were seeing right now, I also have four different comp views.

And the top one, by the way, is the sharpened version of the image. And then the next one down is the sharpened version of the Gradient image. And then next we have the sharpened version of the Noise Removal Image. And then finally, we have the sharpened version of the Gradient Noise Removal image, just so you know what's going on here. Now, I am going to turn all of these comps off, except for the top one, comp 1. And this happens to be a Smart Object. If I click this down pointing arrow, we will see that it's a Smart Object with a Smart Filter assigned to it, and that Smart Filter happens to be Smart Sharpen.

How smart is that that? Now just in case you have limited familiarity with Smart Objects, or you've never even used them before, don't worry. I am going to introduce you to Smart Objects over the course of this series because they are integral to understanding what's going on with sharpening. You can really make great use of them. The great thing about working with a Smart Object is that I can change the settings of the Smart Filter that's applied to it, which happens to be Smart Sharpen, as I was saying. So double-click on the words 'Smart Sharpen,' if you are working along with me, to bring up the Smart Sharpen dialog box. And there are the settings I was telling you about: Amount and Radius.

Now there is a lot of other stuff going on inside this dialog box. Don't even look at it. We are not interested in anything else but Amount and Radius at this point. Now the Amount value is fairly easy to understand. It's the amount by which the contrast has been enhanced inside of the image. So right now we're increasing the contrast, the Edge Contrast, to the tune of 250%. If we wanted to further increase the Contrast and thereby add more sharpness to the image, then we would increase the Amount value. Now it's very unlikely you are going to want to go this high.

This is the maximum value, 500%. And it ends up oversharpening the image terrifically. If you want less sharpness, you would increase the contrast of the edges by a lesser amount, such as, let's say 30%. That still produces an effect. If I click-and-hold on this Preview here, this is the before version. And this is the after version. Not much difference, but there is a little bit of difference going on there. We'd be able see it more at about 100%. So this is the before version right there with no sharpness applied, and this is the after version.

Now then, let's go ahead and zoom in on the image, both in the background, which I did by pressing Ctrl+Plus or Command+Plus on the Mac. I'm also going to zoom in inside of the dialog box here a little bit, like so, by clicking on that Plus button. Let's go ahead and reset this Amount value to what I had before, 250%. And let's discuss Radius. Now I was telling you that the Sharpening filters inside of Photoshop, they produce halos. And so we are drawing dark halos around the dark side of an edge and light halos around the light side of the edge. The thickness of those halos is determined by the Radius setting right here, and it's called Radius, because what Photoshop is doing is scrubbing a halo around each and every pixel.

That's not what it looks like it's doing, because it ends up reconciling into a full image, but it's scrubbing around each and every pixel to the tune of this Radius value. But for our purposes, it's the thickness of the halo, approximately. So notice if I increase this Radius value, then I'm going to increase the thickness of those halos on either side. So, thick dark halos on the dark side, thick light halos on the light side. If I were to take his value up to 12 pixels, then we would have 12 pixel halos, m?s o menos. And the reason I say that approximately is because there is actually a Gaussian style distribution that's associated with this Radius value.

So it shakes out to be more like 14 pixels, but, you know, like you would notice. It doesn't really matter that much. It's approximately the value that you enter in here. And you can see that it's slowly dropping off. So the halo starts very dark indeed and then drops off to nothingness by about this point here, by a little more than 12 pixels out from that edge. And it's a blurry halo. It's like an outer glow, almost. And it is in fact a Gaussian Blur, in the case of the effect that we are seeing right here.

If you want to, you can either associate a high Amount value with a low Radius value. If you want to get a true sharpening effect that's what you do. And so you can go as low as 0.3 pixels. Anything lower is not going to resolve, so you need 0.3 pixels or higher. And this is what the image looks like originally. Notice that I am clicking and holding inside the Preview. And then when I release, we see the after view right there. And so high Amount with low Radius produces super sharp edges. And we'll discuss what that means in more detail over the course of this series, because you don't want to go this low, 0.3 pixels, when you're printing the image, but it's great for screen work.

By the way, you can combine a high Radius value, such as 12 pixels, with a low Amount value, such as 25%, and you are going to get an edge contrast enhancement effect. This is before. And this is after. So we've got some contrast going on right around the edges and this is what's known as clarity, as opposed to sharpness. All right. I am going to go ahead and click OK to accept that modification. And just so you can see the difference here inside of the Image window, this is what the image looks like without that Smart Sharpen filter applied. And this is what it looks like with Smart Sharpen applied, with a low Amount and a high Radius value, thereby producing clarity. All right.

Let's turn off the comp 1 layer and turn on comp 2, which is the Gradient version of the layer. And we are not going to be taking a look at the other two comps. This is where we are going to end. But I do want to you to see the effect of some of these settings when we're working with gradual transitions. So I am going to go ahead and click this down-pointing arrowhead to expand the layer so that we can see the Smart Sharpen filter that's applied to the smart object. I'll double-click on Smart Sharpen here, in order to bring up the Smart Sharpen dialog box. Notice that I have the Amount value cranked up to 500% now.

Let's now take the Radius value up to 12 pixels, so that we can see what happens. And notice now, you can really see that halo, and you can see how it tapers away to nothingness. So it starts very thick indeed and tapers gradually over the course of this gradient to nothingness at this point when the foreground and the background begin to match each other. Same with this light gradient as well. It's tapering to nothingness. And then of course, because the gradients switch, the halos switch as well.

We go from a light halo right there to a dark halo on this right side, and we go from a dark halo on the left side to a light halo on the left side. And we end up tapering right at that location where the colors begin to merge, where the luminance levels become the same. And I'll go ahead and click OK in order to accept that effect, so that we can end with this. And this gives you a real sense of what's going on. So the amazing thing about Photoshop is it's producing sharpness by creating soft blurry halos on either side of the significant edges inside of an image.

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