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The elusive alpha channel remains one of the most misunderstood yet powerful tools in Photoshop. Alpha channels are collections of luminance data that control the transparency of an image, and they inform just about every aspect of Photoshop. As he builds transitional blended layers, fashions a depth map, makes edge adjustments, and takes on extreme channel mixing, Omni Award-winning expert Deke McClelland teaches Photoshop users that where there's a will, there's a way. Photoshop CS3 Channels and Masks: Advanced Techniques covers mapping texture on an image, turning flesh into stone, using vector masks, working with all different channels, creating a rustic edge effect, and much more. Exercise files accompany the tutorials.
Download Deke's customized keyboard layouts for Channels and Masks from the Exercise Files tab."
Here we go last exercise in this chapter, in which we are going to select the beak of the beast using yet another Calculation. But, this time, it's not going to be a simple difference mask and it's not going to be a simple screen function either that we are using to combine mask together. We need to do something more deliberate, something more crafty basically. So it's fitting that we are working inside of an image called Calculated bird.tif that's found inside of the 16 Tough Stuff folder. You may recall that this is a Macaw, and the Macaw has all sorts of different luminance levels going on in the different color channels, and this is red and this is green and this is blue. So they are very different looking channels, but something doesn't change very much from channel to channel that we need to select, and that' the beak. Notice the beak stays pretty much the same, it gets kind of darker from one channel to the next, but that's about it.
So we are not going to be able to use a difference mask to find the difference between a couple of channels. Instead, what we are going to do is we are going to subtract one channel from another. Add and subtract come to the rescue for stuff like this. So I am going to press Ctrl+Tilde or Command+Tilde on the Mac to return to the RBG image. Then, I am going to go up to the Image menu and choose Calculations. This time around, I am going to try the green channel which has a high degree of contrast, and the blue channel which also has a high degree of contrast because red is pretty flat where this image is concerned. I am going to set the Blend mode to subtract, and I am going to look at it and go, Hmm! Well, for one thing, we have got a problem that the last time I applied you say is an Offset value of -20.
So let's go ahead and see if we can raise that a little bit. That's didn't really help. We just have this little sort of sliver sitting right there. So let's try inverting something. This is what you do. Try inverting the Green channel. No, that didn't really help. Turn off that invert. Let's try inverting the Blue channel. Yeah, that actually worked out pretty nicely, we get a high degree of contrast. Let's see if inverting green as well helps. No, it doesn't really, gives us a green area right there, but that's not good because we already have that selected from the previous exercise. So turn off Invert and now let's take the Offset value up to 50 in order to expand the brightness a little bit. Now, what I am going to do is I am going to click OK in order to accept this new channel here, and let's go ahead and call it Beak or something along those lines because it is the beak in progress. I want to dodge and burn a little bit. But, before I do, I need to perform something up in inversion.
Now, I have got the Lasso tool selected, and you notice that I have got Anti-alias turned off, so that I don't have to worry about the Anti-aliasing getting in my way here. So I will go ahead and select this region right here and you can see I am kind of doing my usual, not all that careful job of selecting this region. I have selected this top bill now. So that's an Alt+Click with the Lasso on a PC and Option+Click on the Mac, and the reason that we are selecting this particular beak and not the lower half of the beak is lower half of the beak, his bottom lip if you like, is light against a darkish background whereas the top half is dark against the lightish background.
So let's go ahead and invert it by pressing Ctrl+I or Command+I on the Mac, and that's not half bad, it's done a pretty good job of identifying that area. Now, having deselected it by clicking off of it or I guess I could have pressed Ctrl+D or Command+D on the Mac. I am going to go ahead and grab the Burn tool actually, because we have a lot more burning to do than dodging. But, you know what, before I go any further, what I should do is I should apply some Levels. So let's press Ctrl+L or Command+L on the Mac, and I am going to set this Black point value to something like, something here looks pretty good at 100. I am going to take the White point value down to let's say about 180, and I am just trying to give you a sense of how I really work through these images.
I don't have some values setup in advance in my mind. I am just sort of testing them out and seeing how things look in the background. Then, I will click OK in order to accept that modification, and you know what, I should go at this with the Brush tool first. The standard Brush tool, notice that I have a hard edge brush, set to Normal. I will increase the size of the brush a little bit. White is my foreground color. I am just going to click there in order to get rid of that, and I might as well just sort of paint this area away in order to make it nice and bright beak, and I will go ahead and zoom-in a little bit and paint this area away as well. So as long as I have the Brush tool selected, I might as well paint what I can.
Next, I am going to ultimately dodge and burn, but I seem to be in love with painting for the moment. I seem to be I am auto pilot, is just if I can't control myself. My brain and my hand are doing two separate things. My hands win, so my brain just gets to tell my mouth what to narrate here. I sound like an insane person sometimes when I am doing this kind of stuff, but you try training while you are actually masking a macaw, and it's not so easy. All right, I am going to switch to the Burn tool, and now I am going to burn the shadows of course. So let's burn these guys down like so.
Now, I do have a problem which is that darn point of the beak persists, just absolutely insists really on being and we have long left that area so much, now once again, brain and hand not really working together. All right, so let's go back to at hand if you will, thank you. You would think that I am really doing this by the way, you would think that I am like narrating something I've recorded a long ago, but I am really working through this. I am just, not always working through it, effectively, look at this, look at me select things, and not even tell you what I am doing. I am going to go ahead and select this area right there, and move down like so.
What I want to do is invert it, because this black area should not be black, it should be white because it's inside the darn beak. So let's press Ctrl+I or Command+I on the Mac in order to run the inversion, and probably what I am going to have to do at this point is do a little building because I have got some sort of weak detail to work with here. So I am going to go ahead and grab my Brush tool. I am going to go ahead and press Ctrl+D or Command+D on a Mac in order to deselect that area. And I am going to press the X key in order to make the foreground color black, and I have got my Brush tool selected. I am going to go ahead and click here, and Shift+Click here, and work my way up the bill once again.
Now, this would be a pretty obvious application of that path. I had created earlier, you wold probably want to work with that once again. But this image doesn't contain that path, you would have to draw it yourself if you want to, or go to the image that does contain the path which is any of the other Macaws by the way, and copy and paste it into this image. So that would work as well. Press the X key in order to switch the background color, given what I am doing right now, and I am going to paint this stuff away. So it's all good. I mean whatever approach you take as long as it gets the job done, is going to work for you. Really actually, I could go ahead and switch over to like the Magnetic Lasso tool if I wanted to, or I could try my hand at using something like the new Quick selection tool would probably get me a halfway decent result.
But, as long as I am almost done with the beak at this point, I might as well just go ahead and finish it up using the Paint Brush. And let's go ahead and paint right there as well, and I am just imagining that's what this looks like, because I am masking this darn animal for the 100,000 time at this point. All right. Let's go ahead and paint this away. Now, the question becomes, assuming that I have got a good beak going at this point, and I feel like I have got some good beak, and I am going to by the way Alt+Click down here in order to get rid of this stuff and send it to black because I don't want to be troubled by this later. This should all be black of course, and I will just come down here and grab it.
What do I do, how do I merge this good beak? Press Alt+Backspace or Option+Delete in order to fill that with black. How do I merge this good beak right here, this good beak info with this Alpha 1 info right there. I should actually call this one G+R Stuff because that's what it is. It's combination of Green stuff plus Red stuff, it's the G+R stuff. How do I combine the beak with it effectively? Well, once I get done messing around with the beak, once again hands on its own, got a mind of its own that is to say. Once I get done with that, then I probably go ahead and select this region sort of roughly like this. Go ahead and select around here using the Lasso tool, and so this is the area that I want to add to this image right there.
I just want to add this and I probably go ahead and add this region too since it might look better inside the beak channel; let's check. No, doesn't look any better, so undo that. This area kind of looks better. So let's go ahead and grab it. Then also it look like I had some better tuft info right around here. So I will Shift+Drag around that with the Lasso tool. Let's go ahead and check that. Yeah, that goes ahead and closes that is to say all of this bad beak info. Now, let's go up to the Image menu. Let's choose the Calculations command. We want one of the channels to be G and R stuff, we want the other channel to be beak of course. We don't want to be using any blend mode, that is to say we want to set this to Normal. So we just want the Normal blend mode. I suppose that is a blend mode, and we want to turn on Mask, and we want to mask things inside of which channel? The Selection, not really a channel, but the Selection is of course a temporary Alpha channel. We know that from way back when. and let's go ahead and invert that selection and that way, we are keeping the beak and marrying it with the best of the G and R stuff and we will click OK. So that this makes sense.
We have got channel G and R stuff, channel beak, Normal, 100%, mask inside of the selection, invert, and click OK, and we get this alpha channel right here which is looking pretty darn good. Now, I am not going to finish this up, as I said, we are not always going to finish these masks. I finish that very first one. So I think that's good enough because otherwise, I am going to go criminally insane trying to mask this entire image over and over for like the umpteenth time now. But again, my hand just is on Auto-pilot just for finishing the mask. That's just what I do. I just, once I get in masking mode, I just can't help myself. What you are going to do.
So there you have it, a bunch of different ways to approach a mask inside -- a very tough mask, inside of Photoshop. One of those ways is definitely going to work for you. So remember, when you have got a complicated foreground subject against a fussy background, against a busy background, remember your options which are to go out at using Arbitrary Maps, to go out at using the High Pass filter or to go out at the smartest way really possible here, which is to apply the Calculations command, multiple variations of the Calculations command here in Photoshop.
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