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Alpha channels are collections of luminance data that control the transparency of images, and they influence just about everything in Photoshop. Coming to terms with alpha channels, also known as masks, is a surefire way to maximize results. Omni Award-winning Photoshop expert Deke McClelland leaves no pixel unturned as he explores Refine Edge, Color Range, the Channels palette, the Quick Mask mode, channel masking, blend modes, and more. After watching Photoshop CS3 Channel and Masks: The Essentials, even the most complex techniques will seem like child's play. Exercise files accompany the tutorials.
Download Deke's customized keyboard layouts for Channels and Masks from the Exercise Files tab."
Now that we've seen how you can smooth out the edges of the selection using antialiasing, let's see how you can soften or even blur the edges of the selection using the Feather function. Now when you're using any selection tool except for the Quick Selection tool, you will see a feather option up here in the Options bar, that will be your first option in the Options bar in fact. That is a static control, meaning that it affects the next selection outline that you draw. I don't recommend you use it. I recommend you leave this feather value set to zero at all times, because there is a better way to feather a selection outline using the Feather command, and it's just as accurate. Unlike antialiasing you can apply feathering after drawing a selection.
All right, so I'm once again working in the original version of The big eye.jpg file, that's found inside the 03_select_essentials folder. I'm going to switch over to the Elliptical Marquee tool, I'm going to draw a fairly large selection around the entire pupil inside of the iris so that I can create something that vaguely resembles a dilated pupil, as you'll see, is very vague. We're just doing this for illustrative purposes, we're not trying to create an actual good looking effect. Then I'm going to go up to the Select menu, I'm going to choose modify, and I'm going to choose Feather. Now this is one of two ways you can apply feathering inside of Photoshop CS3. You can either do it from the Feather command, or you can do it from the Refined Edge command. The Refine Edge command turns out to be a little more accurate in that you can preview the effect before you apply it. I'll be showing you Refine Edge along with its various options inside of the next chapter, but for now I want you to go to the old style function, Modify, Feather. You've got a keyboard shortcut of Ctrl+Alt+D here on the PC, on the Mac Cmd+Option+D by default brings up the dock at the bottom of the screen or the right hand side of the screen or what have you. You're going to have to change that if you want to take advantage of Cmd+Option+D for feathering inside of Photoshop, you're going to have to change Apple's default keyboard shortcuts using the system preferences.
I'm going to go ahead and choose the command manually however and I'm going to change that feather radius value to something along the lines of 24 pixels let's say, nothing special about that value and what this is saying is go ahead and blur the selection outline 24 pixels out and 24 pixels in, so big old blur. Now that's a little bit of an exaggeration. I'll be telling you why it's an exaggeration shortly, but for now just go and enter 24, click ok, and then press the D key to ensure that your foreground color is black and press Alt+ Backspace or Option+Delete in order to fill the selection with black, like so. Now I'm going to click off the selection in order to deselect it and you can see if we zoom in there, that we do have a blurry selection outline, a blurry mass of black going on, so a very softly transitions from Black in the center of this pupil area to lighter colors inside of the iris. All right, now, so you get a sense of how you can blur a selection there and you can blur it after the fact as I say, but using that Feather command. Now can you use feathering to somehow simulate the effects of antialiasing. I get that question a lot and the answer is unfortunately no, because they are two totally different operations. I'm going to go and zoom in on this pupil a little bit and I'm going to, still armed with the Elliptical Marquee tool here, I'm going to turn off the antialias checkbox, I'm going to draw a selection, a circular selection right there, then I'm going to press Ctrl+Alt+D, Cmd+Option+D if you get it to work on the Mac, to bring up the feather selection dialog box and I'm going to change this value to something very small like 0.4 pixels, just a fraction of a pixel here and I'm going to click OK in order to accept that result, then I'm going to press the Backspace key, or the Delete key on the Mac in order to fill the selection with white and I'll click off of it to deselect it. Now I'm going to zoom in a little bit so they can see we no longer have super jagged transitions the way we would normally if antialias were turned off. Instead we have a soften version of those jagged edges, but they're not smooth, we still can see the jagged transitions there. Compare that to, if I were to turn antialias on for the Elliptical Marquee tool and draw a new ellipse like so, and then press Backspace or Delete to fill that with white, click off of it to deselect it, that is a truly smooth outline right there as a function of antialiasing compared with this jagged soft outline. That's the function of turning antialias off and applying just a smidgen of feathering.
All right, one more thing, I want to tell you about the galcian transition that's associated with the feathered outline. I'm going to turn antialias back on as it is, I'm going to draw a new selection outline, a bigger one here, like so, down here in the lower left region of this strange pupil effect, I'm going to feather it, by pressing Ctrl+Alt+D, Cmd+Option+ D on the Mac and I'm going to change this feather value do let's see once again 24 pixels and I'll press the Enter or Return key in order to accept that effect, then I'll press the Backspace key or the Delete key on the Mac in order to fill the selection with white and let's go ahead and zoom in here. Now as I was saying, we are approximately blurring the selection outline 24 pixels out and 24 pixels in by virtue of the fact that I enter 24 for the feather radius value, but not exactly. We have what's known as a galcian transition in effect here and what that means is that at first, the blur runs very, very slowly right at the beginning of the blur on the outside edge and the inside edge of the blur goes very slowly, then it goes very quickly through the middle region of the blend and then it smooths out and it goes very slowly at the last edge of the blend here, the outer edge of the blend both outside the selection outline and inside the selection and that ensures that we don't see a sharp edge around our blur and I know that sounds just crazy, that somehow we would see a sharp edge but if we performed a linear blur in which every single bit of this blur got the same amount of weight then we would actually see the physical edge of that blur, where it started and where it stopped and that would defeat the purpose of the blur in the first place, so as a result, the blur gets sort of pushed out a little bit and a 24 pixel blur ends up turning into about a 25, 26, 27 pixel blur. You should just be aware of that, if you're trying to blur within a very specific space. Anyway that is how blurring works, how selection blurring works inside of Photoshop using the Feather option. In the next chapter we're going to take a look at how each and every one of the selection tools work and how you work with them for maximum effect.
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