Understanding amount and radius

show more Understanding amount and radius provides you with in-depth training on Photography. Taught by Deke McClelland as part of the Photoshop CS3 Sharpening Images show less
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Understanding amount and radius

In this exercise we are going to see how you can adjust the degree of Sharpening that's applied to the image using a couple of different numerical values. Now there are a variety of different filters that are available to you where sharpening is concerned, there is Unsharp Mask, Smart Sharpen, High Pass, Emboss, even Gaussian Blur as it turns out. Now every one of these filters works differently, but most of them sharing in common ad Amount value and all of them sharing common something analogous to a Radius value. So we're going to see how those amount and Radius values work.

Well take a look at the specific filters and the application of those filters in a later Chapter. For now notice that I am still working inside of the Sharp Shapes.PSD image, found inside the 01howitworks folder. I've got my Standard Layer Comp active, I am going to go ahead hide the Layer Comps palette and I am going to bring out my Layers palette. I am going to expand my palette so I can see the Layers palette down here. If you are looking at your Layers palette too, you should see a series of four Smart Objects comp #1, comp #2, comp #3 and comp #4, as well as this group called the ingredients.

We are most interested in these comps here, these Smart Objects to which I have applied editable Smart Filters. Now if you're not sure whats going on with Smart Objects and Smart Filters or you have limited experience with them, don't worry. I am going to show you how they work in detail in the later Chapter, but for now I want you to notice that comp #1 is the sharpened version of the standard image, whereas, I'll turn it off and turn on comp #2, which is the sharpened version of the gradient image with texture, notice that. Then comp #3 is a smooth version and sharpened as well of the standard image, and then finally, we've got comp #4, which is a smooth and sharpened version of the gradient image.

The ones that we are going to work on, we are going to be playing around with comps #1 and #2 here. So go ahead and turn comp #1 on, and I am going to switch to the full screen mode so that I have a little more room to work. I am going to twirl open the comp #1 item here by clicking this down pointing arrowhead over here in the right-hand side of the Layers palette and that reveals my Smart Sharpen filter. So I have sharpened this image using Smart Sharpen,. To adjust its settings go ahead and double-click on Smart Sharpen and you'll see right away the Amount and Radius values.

So several other options going on inside this dialog box. For now all we are concerned about is Amount and Radius, and here's how they work. Amount controls the amount of sharpening you apply. It's pretty easy to understand, pretty easy to get a sense of whats going on. All you do, if you need more sharpening, you increase the Amount value and that gives you more of a tactile, more of a crunchy fact. And if that's too tactile or crunchy, as it obviously is here, then lets go ahead and take the Amount value down in order to create a more subtle effect.

For Now I am going to leave the Amount value set to 250% so we can focus on the slightly more difficult to understand option, which is Radius. It also happens to be the more important option where sharpening is concerned. Radius defines the size of the halos. Lets go ahead and zoom in on this preview, this in dialog box preview right here, move it down a little bit. You can see of course that we have a dark halo tracing the dark side of the circle and a light halo tracing the light side of the circle. The size of that halo is defined by the Radius value.

So right now we have one pixel on the outside and one pixel on the inside. Now it's called Radius because Photoshop actually goes through and scrubs around every single pixel, so it's scrubbing in these tiny little circles all over the place and the size of those circles is defined by the Radius value. But where we are concerned, it ultimately defines the size of the halos. So I am going to increase this Radius value, lets say to 12 pixels and you'll see that our halos grow in size to 12 pixels, they're all soft halos. So notice that the halos are dissipating, or dispersing really, over the course of these 12 pixels.

Now Photoshop tends to use a Gaussian distribution curve for this softness, and that means that the halos are actually a little bigger than the Radius value. So these halos are more like 14 pixels in size. But it doesn't really matter that much exactly how big they are. We are more interested in the visual effect. Now in this case I'll go ahead and move my dialog box so we can see this for a moment. Its not really a sharpening effect at this point; we are getting more of a high-contrast edge effect, so we are definitely sharpening the heck out of this texture in the background.

But where the big objects are concerned, they don't tend to look so much sharp, just rounded, almost contoured, shaded if you will. So basically how things work is this way, if you want a true sharpening effect and you want to combine a high Amount value with a low Radius value and you can go as low as 0.3 pixels. You can go even lower than that; it's just that the effect really drops off in the 0.1 and 0.2 range. You really don't see anything until you have this guy cranked up to about 0.3.

But it does make a difference. Notice there. I'll go ahead and zoom in even farther so we can see this at work. I'll go ahead and click and hold on the in dialog box preview. This is what the effect looks like before, unsharpened, and this is what the image looks like after this Amount value of 250% and the Radius value of 0.3 pixels is applied. So we do have a slightly sharp effect applied at this point. You can also combine a very low Amount value. Lets go to just like 25% with a very high Radius value, lets say 12 pixels, and that's going to give you more of a heightened contrast effect.

Allbeit, the contrast is going to be applied to the edges but it's not going to look so much sharp as contrast-y. So I'll go ahead and click OK in order to accept those values, once again they are 25% and 12 pixels, I'll click OK, and just to give you a sense of what kind of difference this makes, lets go ahead and zoom in just little bit here and I'll turn off this Smart Sharpen filter by clicking on its eyeball. This is the unsharpened version of the image; this is the sharpened version of the image. So slight modification there. Now lets take a look at combining Amount and Radius with the gradient version of the image.

I am going to turn off the comp #1 Smart Object and turn on the comp #2 Smart Object so that we can see the gradient version of here. I'll go ahead and open it up as well, expand it so that we can see the Smart Sharpen item. Lets go ahead and zoom out just a little bit so that we can take in more of the image at a time, and I'll double-click on the Smart Sharpen. Lets not worry so much about the Amount value. You notice that it's cranked through the roof right Now it's 500%. Lets just go ahead and raise that Radius value once again to 12 pixels and click OK order to accept that. And now you can see if we scroll to the top we have a very, very dark black, thick halo at the top on the inside edge of the serpentine line.

Up there toward the top of the image, we have a white halo on the outside of course, and notice that they are growing slimmer and slimmer as we work our way down to where we are almost losing the Radius entirely at this point. Of course, right there we have very little in a way of any halo occurring at all because we have very little in a way of a difference between the line and its background, and of course the light halo is also dissipating over time and then they switch places and they flair out once again toward the bottom area of the image.

So that's how it's working. And you might think of the Radius as being a blur because that's what it really is, it's a blurred halo that's been drawn around the image and that's the way Sharpening works inside a Photoshop. Photoshop uses blur, specifically Gaussian Blur in most cases, in order to create the effect of sharpening, as strange as that sounds. So now that's the overview of how Sharpening works inside of Photoshop. In the next exercises we're going to see how you can gauge the sharpness of an image on screen.

I'll start things off by showing you how you can measure your monitor's resolution.

Understanding amount and radius
Video duration: 7m 50s 10h 36m Intermediate


Understanding amount and radius provides you with in-depth training on Photography. Taught by Deke McClelland as part of the Photoshop CS3 Sharpening Images

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