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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."
Now that we've created the difference mask using the Calculations command and we have enhanced the contrast using an arbitrary map that we've applied using the Curves command. We are ready to take this rough Mask this approximation of the mask, here, to turn it into a real mask that outlines all of the Flesh tones, so specifically the hand because we really don't have too much information to work with where the pen is concerned. So steps one and two are going to apply the Burn and Dodge tools in that order actually. And then we're going to apply the Gaussian Blur Filter and then we're going to turn around and apply Levels and that should give us the final Flesh mask here.
I am working inside of a catch-up document called Difference mask.psd. You can open it from the 16_Tough_Stuff folder if you want to and then switch to the Difference channel. I am going to go ahead make a copy of this channel and I am going to call it Flesh Mask since that's what it's going to be of course. And now let's set about enhancing this mask. I'll switch over to the Burn tool which is where I want to start, make sure that you have a fairly large cursor as I do here that it's nice and soft, that the exposure is set to 50% and the Range option is set to Shadows. And now I am going to go ahead and zoom it a little bit on these shadow details right there and I am going to paint them away.
It might take a few passes in order to get rid of all those little bits of garbage there and then I am going to paint down here at the base of the palm as well. And that should pretty much do it. There is not too much action out here in this region although you can just make sure by painting along. Actually we do have a little bit up toward the top. A little bit of lightness toward the top of the image that you might want to paint away. You don't need to worry too much about the pen nib by the way or any portion of the pen actually. All right, so I am just painting around in outside just to make sure that every thing has gone as it needs to be. All right, now let's switch over to the Dodge tool and I am going to do that just by pressing the O key because I have my keyboard shortcut set up to skip the Sponge tool there.
And once again, I have a large blurry cursor I have got Range set to Highlights this time, Exposure to 50% and I am going to paint away the palm, that hairy area of the palm, down there the whiskery area, don't you know. And you may find that it takes quite a few passes in order to get rid of all that stuff. Now it's not essential that you get rid of every single little bit of material there. And you can leave a few straight pixels behind if you want to. It's not really going to affect things too much. You could also paint over this area if you wanted to but it's not necessary.
Here's how we're going to take care of the pen. We're going to grab the Lasso tool not surprisingly. And I am going to go ahead and Alt+Click around this region. This would be Option+Clicking on the Mac in order to select this region of pen right there and then I am going to dig in very tight to this area and there is a little bit of sort of vertical area that I want to keep. And then I will eventually Alt+Click my way around. I still have the Alt key down of course, so the Option key on the Mac. And when I release Alt or Option I will generate the selection as I have done right there. I am going to press the D key in order to establish my default colors and then I will press the Backspace key or the Delete key on the Mac in order to fill that area with black.
All right, so that looks good. Now let's go ahead and deselect that previous selection then Alt+Click around this region of the pen, the shaft of the pen here and that's an Option+Click of course on the Mac. Notice that I went in from the knuckle a little bit. So I am cheating inward. I don't want to select too much information there. I would rather select too little at this point because we're going to be selecting the pen in a separate pass. And I'll go ahead and press Alt+ Backspace or Option+Delete to fill that area with white. Then I will deselect the area again. Deselect that portion of the image and I am going to Alt+Click like so around the top of the pen. That would be an Option+Click on the Mac in order to select the top region and then I'll fill it with black by pressing the Backspace key or the Delete key on the Mac.
Now you can see that this region is pretty junky and I am not worried about it at all, because that all falls inside of the pen which we will select later. All right, this looks good to me; the only problem at this point is that we have some rough and kind of rotten transitions. Now I was telling you in previous chapters that when you are trying to select a blurry area of an image, noise tends to be your friend because the noise is inherent in the blur that's captured by a digital camera. But in our case I want to cheat the mask in a little bit. So I am going to blur that noise away and then I am going to apply the Levels command in order to choke the mask inward.
So here is what we're going to do. I am going to actually go ahead and look at the RGB image at the same time by clicking on its eyeball there. Let's go ahead and change the color of the Flesh Mask, so that we can see it a little better by double-clicking on Flesh Mask. Then let's change its Hue value to 210, let's say and click OK. And a little bit more opacity would probably do well. And I'll click OK in order to accept that result. And we can see how the mask traces along the edges of the hand. It does a pretty good job but in places, it's a little iffy like you know little rough and weird looking up top here. So let's go ahead and apply the Gaussian Blur command. I am going to the Filter menu, I'll choose Blur and I'll choose Gaussian Blur and I am going to change the Radius value to 6 pixels. You can enter 6.0 if you like and then click OK.
Now we've got a nice soft edge that we can move back and forth using the Levels command like so. I am going to go ahead and press Ctrl+L or Command+L on the Mac to bring up Levels. And I'll go ahead and move the image over a little bit so that I can see how this edge transitions along the thumb and the finger. Let's go ahead and raise the black value to 80, in order to choke the edges inward and then let's expand the edges ever so slightly by taking the white value down to 215. So 80 for black, 215 for white leave Gamma set to 1.0 and then click OK in order to accept those new edges. And thanks, are looking pretty darn good folks.
This provides us with a little bit of soft edge, a little bit of highlight on top of the thumb and the forefinger and so on. And we also have a little bit of highlight on the underside of the third finger here. That's all good news, so let's go ahead and implement this mask, I want you to Ctrl+Click or Command+Click on the Alpha channel, then press the Tilde key in order to hide the RGB image and then press Ctrl+Tilde or Command+Tilde on the Mac in order to go to the RGB image. Switch over to the Layers palette here. Make sure that the hand layer is active and let's go ahead and assign this selection as a layer mask by clicking on the Add a layer mask icon down at the bottom of the Layers palette. And there we have it; we have managed to do a really great job actually of selecting the Flesh information in this hand. We haven't done such a hot job of selecting the pen yet, but that will come. So your image should look like this right here, it looks pretty darn good.
Still a few changes that we have to make. We will begin masking in the pen in the next exercise.
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