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In this exercise, I am going to explain how to use Tolerance and the other controls that are available to you in the Options Bar when you're using the Magic Wand tool. All of these features control the behavior of the Magic Wand the next time you use it. So for example if I were to change my Tolerance value from 32 to 80 while I've got a selection outline going here inside my ManlySaw.jpg file, and then press the Enter key or the Return key, I might naturally expect to expand that selection to include more similar colors inside the image, but nothing happens.
And that's because it's not a dynamic control, it affects the next time I click, and in fact I'll go ahead and click here below the ManlySaw and I select this time the entire sky except some garbagy stuff up here in the upper right corner including almost all of the saw blade. So I really have expanded that selection outline too far this time. But before I tell you what is the proper tolerance value for this image, let me explain how these options work. I'll go up to this down pointing arrowhead next to the Magic Wand icon up here in the Options bar, and I'll right-click on it and choose Reset tool and that will restore my default settings as you see there.
Then I'm going to go ahead and switch to this image here Gradients.psd found inside the 08_selections folder, and it features two identical black to white gradients divided by a red bar here on the Background layer. So make sure the Background layer is selected. There is also another layer, it's called red bars that's currently turned off. The Tolerance value controls how far Photoshop expands your selection in luminance levels. So if you recall my discussion of luminance levels in the previous chapter, 0 means black and 255 means white.
Therefore you have 256 luminance levels on a channel by channel basis inside of a standard 8-bit/channel image. If I go ahead and click somewhere near the center of this gradient, then you'll see that Photoshop goes ahead and expands the selection 32 luminance level lighter and 32 luminance levels darker than my click point, and that happens on a channel by channel basis and then Photoshop finds the average of those channel by channel selections, and delivers it to you here. In our case, we're looking at a black to white gradient, so we don't have any differences between our various color channels.
Now if you want to change the size of the selection you would go ahead and change that Tolerance value. So for example, I'm going to press the Enter key, or the Return key on the Mac, which automatically selects the first numerical value up there in the Options bar, which in our case is Tolerance, and I'll change it to say 80 and then I'll press the Enter key, or the Return key on the Mac, and I'll click on a similar color down here in the lower gradient, and notice how much bigger this selection outline is, because it's expanded 80 luminance levels lighter and 80 luminance levels darker than my click point.
The next option in the list is Anti-alias which goes ahead and tries to smooth out the perimeter of the selection. You may recall the anti-aliasing that smoothed out the elliptical marquee that we originally drew around the moon. Well this is a little different this time and a lot less successful. In fact, the edges that you get with the Magic Wand tool converge on absolutely jagged as they are in this case here, because what Photoshop does is it selects, say, 80 luminance levels lighter and then 80 luminance levels darker and then it just stops.
It abruptly stops at that outline, throws in a little bit of anti-aliasing and that's all you get. Just so you know, you are going to get some brittle edges with the Wand tool. Now the next option, Contiguous might be better called adjacent. And what it does when it's turned on Photoshop only selects adjacent pixels, pixels that neighbor each other. So in other words, it doesn't jump this red gap right here. If you wanted to jump the gap then you would go ahead and turn Contiguous off and then I'm just clicking at a different location up here in the top gradient.
Notice that I select 80 luminance levels brighter and 80 luminance levels darker inside the top gradient and that exact same region of color down here in the bottom gradient, because I permitted the wand to jump the gap. Then we have this option here called Sample All Layers, I'll show you how that works. I'll turn on the red bars layers so that we can see it, but by default Photoshop only affects the active layer. So if I click here for example, then I select 80 luminance levels lighter and 80 luminance levels darker than the click point and because I have Contiguous off it jumps the gap but notice that while the Magic Wand tool is paying attention to this red bar, it's not paying attention to the top or bottom bars because they're on a different layer.
If you turn on Sample All Layers and then you click somewhere inside the image, then it will take into account everything that you see on screen that is to say the composite view of the image, and therefore it neglects to select every one of these three bars. But it's important to note, a selection in Photoshop only affects one active layer at a time. Now something I just want to throw in here for fun is that a terrific use for the Magic Wand tool is to select a region of solid color.
For example, let's say I want to exactly select this bar without introducing any sort of soft or smushy edges. Why then I would go ahead and turn off Sample All Layers, I would turn on Contiguous, I would turn off Anti-alias because otherwise I am going to get smushy edges. And I would set the Tolerance value here to 0, and this combination of values allows you to select a single region of color like so and that selection that I just created there along that red bar is now exactly rectangular.
Yes I could have drawn it with a Rectangular Marquee tool but it would've taken me a heck of a lot more time to make sure I had everything aligned properly. So just so you know, there are times when the Magic Wand tool comes in exceedingly handy especially for screen work, for high contrast artwork and so on. Let's go back to a continuous tone photographic image however, this ManlySaw image.jpg file. What I'm going to do in this case is turn Anti-alias back on, even though it's not the greatest option on earth and it doesn't assure entirely credible edges.
It does want to be on when you're doing photographic work. And I'm going to change the Tolerance value to 12 for this image. By trial and error I figured out this worked pretty well and then I'll press the Enter key or the Return key on the Mac. Obviously this is a static control so it doesn't change the existing selection outline. I'll press Ctrl+D, Command+D on the Mac to deselect the image and now I'll click right about there and notice that Photoshop leaves that saw blade alone. So it doesn't select that much of the sky but nor does it select something we don't want to selected at this point in the game.
Now I am going to press the Shift key and click again in order to expand the selection outline, and I could keep doing that if I want to or I could take advantage of a couple of automated expansion commands that I'm going to explain to you in the next exercise.
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