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Photoshop mastery can be elusive, but in Photoshop CS4 One-on-One: Mastery, best-selling author and video trainer Deke McClelland teaches the most powerful, unconventional, and flexible features of the program. In this third and final installment of the popular and comprehensive series, Deke delves into the strongest features that Photoshop has to offer, including scalable vector graphics, Smart Objects, and Photomerge. Exercise files accompany the course.
Recommended prerequisites: Photoshop CS4 One-on-One: Fundamentals and Photoshop CS4 One-on-One: Advanced, both part of the lynda.com Online Training Library®.
Download Deke's customized keyboard layouts and color settings for Photoshop from the Exercise Files tab.
In this exercise I'm going to show you how to create an alpha channel that will serve as the basis for a mask here inside of Photoshop. I'm going to switch over to the Channels palette and I would like you to do the same. Now this image is utterly wonderful for masking purposes because it's got some interesting things going on. First of all, it's a low light snapshot because the camera was set to just auto-functions all around, auto- metering. We have got a high ISO of 800 which means that we have just ton of noise going on the background and it's kind of wormy noise because of Camera Raw's automatic sharpening. So I ran this to Raw, it really didn't pay much attention to the image inside of Raw, I just brought it over, did a little bit of development.
But I did allow the noise to get sharpened a little bit and as a result, we have some sort of warm like texture going on in the background, which is definitely one of the things that Camera Raw tends to do if you don't watch it. Anyways, that's okay. We can work with it. We also have a lot of stray hair which is great because this is the kind of thing that Photoshop just excels at selecting masking is terrific where hair is concerned. So if you have light hair against the dark background, as we do, or dark hair against the light background, even if it's only occurring in a single channel inside of the image, then you are in great shape. That means you can select that hair.
So a lot of people are scared of hair, rightly so, I mean it looks like will be extremely complicated to select all of this junk, and of course, if we are relying on any of the selection tools, we'd never get anywhere with it. We are not going to trace around these hairs with the Magnetic Lasso tool, for example. And we are really not going to do it with the Color Range command either because it tends to exaggerate the hair details and kind of clump them up. What you want to do instead is create a journeyman alpha channel here inside of the Channels palette. But you need to choose the right channel in the first place from which to build your alpha channel.
So here we are in the Channels palette, you can see that I have got RGB composite image, which comprises the Red, Green and Blue channels. So RGB is not a channel in and of itself, it's the composite blend of the channels that follow it. And then we have two extra channels; these alpha channels right here called Partial Mask and Final Mask and if you were paying attention in the previous exercise, you may notice that we have more channels than we used to have and that's because I just went ahead and added one behind the scenes between exercises there. The reason being when I was actually creating my web graphic, I didn't worry about the lower section of Russell here, I just worried about the portion of his head and his hand that were going to be above the marquee but I figured as long as we are here in masking, as long as we are doing a project, we might as well do it for real. So I went ahead and masked all of the flesh and the hair away from the background. I didn't worry about the shirt; the shirt would be a completely different beast in terms of masking. It would be possible but because it's dark on dark, it would be a little more complicated.
So that's the high irony of masking folks. It's that something like hair; these filigree details as long as you have good contrast definition there, no problem. It's when you start running out the contrast then you start having problems inside of Photoshop. So fabric details are typically more difficult to select than hair. If you want to learn all about the stuff, please checkout My Channels and Masks series here on the Lynda.com Online Training Library. What we need to do is to find the channel that is going to enable us to take the image and use the image to select itself and that is what masking is all about. You are trying to trick Photoshop into seeing what you are seeing; you can't just click on Russell and select him.
However, you can use Photoshop's way of seeing the image to your advantage in order to use the image just I say to select itself. So why don't we go about doing that? Well we want to find a channel inside the image that already gets us a large portion of the way there. So we are going for this. This is what we want. We want Russell totally white to indicate that he is selected against the pitch black background to indicate that he is totally deselected with some nice sort of anti-aliased edges around Russell and these edges are what really sell the effect, it's not about the interior, it's not about the area that's not selected, it's all about these edges right there. So you want some grayness in the edges.
So let's go ahead and zoom out again. Which channel resembles this the most? Well let's go back to the RGB image for starters and notice that we have got these keyboard shortcuts. So you can either click on a channel to see the channel to select it or you can use a keyboard shortcut and these keyboard shortcuts have changed since Photoshop CS3. So it's CTRL+2 or Command+2 on Mac to see the Composite image. It's Ctrl+3 or Command+3 on the Mac to see the first channel, which is in this case is the Red channel. It's Ctrl+4 or Command+4 on a Mac for the Green channel and then Ctrl+5 or Command+5 on the Mac for the Blue channel and they are all listed right there so you can't help but remember them.
Notice that he looks very high contrast in the Red channel. He does have quite as much contrast in the Green channel. So he is very white in the Red channel against a fairly dark background. The background is fairly similar in the Green channel but he is darkening up and then by time we get to the Blue channel, the background is darkening a little bit but Russell is darkening like crazy in the Blue channel. This isn't Russell, not resonating well in the Blue channel, this is all of us and especially under low light like this we are just noise like crazy creep up in the Blue channel. When things start going wrong inside of an image, it's the Blue channel that suffers first and suffers foremost and then the other channels start trailing behind it. You are going to look in the Green channel but you are going to look best in the Red channel. Why? We are all different luminance levels essentially of orange, which is mostly red with a little bit of green. Not much blue at all.
All right, so that's my long winded way of saying you want to blend the Red channel and the Green channel together, the Red channel and Blue channel together, using this command under the Image menu called Calculations, by spending an entire chapter on Calculations in my Channels and Mask series. And that command is useful when no channel is really doing what you wanted to do; when you have to blend a couple of channels to get to a good base. Anyway, we have already got good channel so we have got red, he is dark in the background, he is light in the foreground, he already looks a lot like the Final mask as you can see. So once you do the first step here, once you have identified the channel that's going to work for you, you grab that channel.
Don't just start editing it because the image relies on that Red channel. For example, I'll just select an area in the Red channel and press the Backspace key to get rid of it. Well that kind of damages the RBG image. So you can't touch that Red channel. You cannot, if you are trying to make some color modifications but you don't want to mask directly. So Ctrl+Z, Command+Z on the Mac, let's go ahead and press Ctrl+D or Command+D on the Mac to deselect the image. Instead what you do is you grab that Red channel and you duplicate it by dragging it on to the page icon down at the bottom of the Channels palette and releasing. Now you have got a copy of the channel, now you can do anything you want with it. This is now an alpha channel that's ready for your editing and I'm going just go ahead and rename it my mask or something along those lines. By double-clicking on its name and entering a new name just as you do with layers and we are now good to go.
By good to go, I mean we are going to begin to build our mask, we are going to increase the contrast to the mask and I'm going to show you how to save an alpha channel along with an image in the next exercise.
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