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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."
In this exercise, I am going to show you one way to build your own custom contrast mode, in which we multiply the shadows and screen the highlights. Now so far I have managed to apply the Overlay mode to this mountain range in front of this woman's face and you may recall from the previous chapter that Overlay combines a half-strength multiply with a half-strength screen. But what if I feel like you know what, the highlights look okay, but the shadows just aren't nearly what I want them to be. I want a full strength or something resembling that in the way of the multiply.
I want more control over the multiplication of my shadows, and it might as well have more control over the screening of my highlights as well and that's what we are about to achieve inside of this exercise. So I am working inside of an image called Bernard & Russ.psd. Named after the photographer who are responsible for the two images that we are mixing here. Kevin Russ shot the Background image, the woman in the bluish goggles and Loic Bernard shot the Dolomites, the mountain range in the foreground here to which I have applied the Overlay blend mode.
Those will be, who have been working along with me, who are with me in the previous exercise will see that I deleted the Bubbles and the Blood Cells layers because we are not going to be using them to create the final effect which is this guy right here, this is the effect that we are going for ultimately. The name of this image is Study in blue.psd. All of these images were found inside of the 10 Advance Blend folder. You don't need to open this image right now. I just want you to see where we are going ultimately and periodically I am going to be showing it you of course. All right, so you might wonder, at this point you might wonder why in the world there isn't a blend mode that combines full-strength multiply with full-strength screen and the reason is because then we would have jagged transitions between the shadows and highlights.
Let me show you I have fabricated such a mode inside of this image right here. Its called Full on M&S.psd. M & S meaning multiply and screen of course and you can see that I have actually multiplied the shadows and I have screened the highlight exactly in the same way the that the Overlay blend mode does except that I have gone with full-strength multiply and full-strength screen instead of half-strength versions of the modes and as a result we have very jagged transitions between the highlights and the shadows.
Overlay by virtue of the fact that reduces the multiply and it reduces the screen. It applies them both at half- strength as I was saying, ensures that we have smooth transitions between the two. Because 50% becomes neutral and so the effects die away right there if that point of neutrality and we get very soft transitions. All right, anyway I am going to zoom back out. You can check out this image or not, it doesn't really matter. I just wanted you to see why this mode doesn't exist inside Photoshop and we are going to have to build it ourselves. But we are going to build it better than that. It's not going to look all choppy like that.
All right, so here is what I want you to do. Let's go ahead and bring back all of our palettes and so forth. I have got the Dolomites layer selected here. I am going to set it to the Multiply blend mode, by pressing Shift+Alt+M or Shift+Option+M on the Mac and I am going to go ahead and name this layer Multiply as well. Now that is too much shadow for me. The shadows are too strong at this point. I want to back them off. So I am going to set the Opacity value to 50% just by pressing the 5 key. And of course, I am assuming that you have a Selection tool active for all of these keyboard shortcuts to work and now I have reduced my Opacity to 50%. Now you might say okay, but isn't that what we had with overlay? Wasn't a overlay a 50% version of Multiply? No it was a half-strength version of Multiply.
If I go back two steps here in order to show you the Overlay version of the image, you will see that it's a very different effect than this one right here and this 50% Multiply is less colorful, it's less blue, it's more brownish, it's about the same darkness, a little darker than the overlay effect was. So it is a different mode, so basically everything is unique inside of Photoshop. I was telling you in the last chapter, all of the blend modes are unique and you can't mimic them just by goofing around with the Opacity value.
That's no way to work. If you are goofing around with the Opacity value, you are going to achieve your own custom effects which is even better actually. That's a good thing. All right, now let's say we also want to screen the highlights. Well then what we would do is we would add a version of this same layer set to the Screen mode. So I am going to press Ctrl+Alt+J or Command+Option+J in order to jump the Multiply layer. I am going to call it Screen by virtue of the fact that I had the Alt or Option key down. I get the New Layer dialog box. So I will Name the layer Screen and I will set the Layer to the Screen blend mode of course and I will change the Opacity value to a 100 %. so we are able to do a lot of work inside of this dialog box with one operation because we press Ctrl+Alt+J or Command+Option+J on the Mac.
Now click OK in order to create that New Layer. That we have indeed instilled some very bright highlights in this image but they are too much, I think the highlights are now officially overwhelming the image. So I could reduce the Opacity of Screen as well to 50% but then we are just going to get kind of this lukewarm effect at this point because basically we are really obscuring the Background layer. Instead, here is what I am going to do. I am going to reinstate the Opacity of 100%. I am going to make the Screen mode subordinate through the Multiply mode and I am going to do that by using a Clipping Mask. So with the Screen layer active, I am going to go up to the Layer menu and I am going to choose Create Clipping Mask, like so.
You can also use a keyboard shortcut if you prefer and that will go ahead and indent the Screen layer. We get this little arrow showing that the Screen layer is masked by the Multiply layer and therefore what's happening is both layers are being calculated together before they are being mixed with the Background layer and as a result we get this effect here. Now it is pretty darn tepid, the way things are structured right now. In fact the Screen layer isn't making that much difference. Here is the image composition without the Screen layer. Here is the image composition with the Screen layer. So it's just making a very slight contribution to the appearance of the image.
Compare that to the final effect that we are looking for in which we have some brilliant highlights going on including a bunch of clouds going on inside of her goggles and that's what we ultimately want. We want this kind of brightness. Whereas right now we are kind of stuck with this effect right here. There is no clouds inside the goggles whatsoever. We need to change that. But in order to get better highlights and better shadows, out of our to Dolomites layer right here, or two mountain range layers we need to take advantage of a function called Luminance Blending inside of Photoshop. So we are going to take a break from this composition for a couple of exercises and I am going to show you how Luminance Blending works beginning in the next exercise.
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