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Based on the device-independent CIE specification from 1976, Lab color is frequently misrepresented as a techy, labor-intensive color space. In fact, Lab color performs certain types of color modifications more quickly and with better results than RGB. In Photoshop CS3 Mastering Lab Color, Deke McClelland explores how to use Lab color "to make bad photographs great and great photographs even better." He demonstrates image manipulations that are best suited to Lab, and walks through a typical, non-destructive Lab correction. Deke also shows how to correct lighting, apply selective color modifications, and reverse the effects of color cast. Exercise files accompany the course.
Hey, I see you are back. Very encouraging, I mean saying you are tenacious which is what I love about you and your reward is going to be a special masking technique that's only found inside this series, nowhere else, at least nowhere else inside the lynda.com Online Training Library. What we are going to be doing is we are going to be merging an RGB channel with the Lab channel in order to create the best base Alpha channel that we could possibly get where this particular image is concerned. So the particular image concerned is Blue shirt man.jpg found inside of the 05_selective folder and we and need to create a mask in order to distinguish his shirt from the background because no other methods are left to us.
We are going to be using the Curves command inside the Lab mode in order to effect our color shift and Curves, by itself, doesn't provide any masking control that we saw that even though Hue/Saturation does provide limited masking controls, they are just not going to work for our purposes. All right, so here's what I want you to do. For starters, and those of you who have worked with me in my Photoshop CS3 Channels and Mask series, also part of the lynda.com Online Training Library, know that when you are creating a mask, you start by examining the channels that are available to you. So this is an RGB image and actually we have Red, Green, and Blue channels, so let's check them out.
Here's the Red channel, now there is a high degree of contrast. Bear in mind, while we are making a mask, we want a lot of contrast. What we are really looking for is the opposite of this; we want a white shirt against the black background but we can change that as easily as just by pressing Ctrl+I or Cmd+I in the Mac in order to invert the colors. So we have a white shirt against a dark background that's great. But you can see now that we don't really have as much contrast as we really need and of course, you wouldn't want to change the Red channel. That's going to fairly mess up the composite RGB image. Yeah, let's not do that.
But this is a good starting point. Green, not so good. We have a little bit of contrast between the shirt and the guy's flesh in the background but we are losing it. We have a lot of shared gray values going on. Then Blue is just no good at all for our purposes because that's where his shirt and the background are the best match. And then, of course, he looks quite gruesome in the Blue channel. I have to say it's not just him, we all look our worst in the Blue channel, but older we get too that's the great thing about it; aging really happens in the Blue channel.
In a perfect world, we wouldn't have Blue, then we wouldn't age. That's my theory because look at me. It looks great in the Red channel. Let's go back to RGB. So we want the Red channel to be available to us but we need the Lab mode to be available to us as well in order to perform this little technique here. So let's go ahead and duplicate them and then convert into Lab. Go up to the Image menu, choose the Duplicate command, and let's just go ahead and call this guy Living large in Lab so that we can find him very easily later inside the 05_selective folder and I'll click OK.
We'll go ahead and zoom in, move him over to the right a little bit and of course, convert him into Lab. That's very important. Go to the Image menu, choose Mode and choose Lab Color. Now we have Lightness, a, and b channels. So let's check them out. There's a Lightness channel, a good looking channel but not enough contrast. It looks a lot like a Green channel, in fact. Here's the a channel. If you have thought he looked bad in the Blue channel, check him out in the a channel. You know what, he is not a spring-fall kind of person; the turquoises and the crimsons don't work for him.
I don't know if those are spring-fall colors but whatever colors they are, they are not his colors. Very, very gruesome indeed but if we go to b, hey he is still looking bad but we've got some contrast going on. We've got a little bit of contrast between the shirt and the background and his flesh. Actually, his flesh is going really light. I have a hanker in here, that if we somehow mix the best of the b channel with the best of the Red channel, we are going to get somewhere. So let's try that out, let's test out that theory. Let's go up to Lab once again, go back to the composite image. Then I want you to go to the Image menu and choose the Calculations command.
Now, Calculations allows you to blend two channels, two channels that are already inside of the image in order to create a new Alpha channel, a base Alpha channel that you will eventually develop into a mask. You can not only blend channels inside the same image but you can blend channels inside different images, different open images as long as they contain the same exact number of pixels wide and tall. So go to Calculations and you'll see up here for Source 1, notice right now, it's trying to multiply the two Lightness channels by each other.
So pretend that they are different layers; Source 1 is on top and Source 2 is on bottom, set to Multiply at 100%. Well we want to start with Red because it's our really great channel. So go up to the Source 1 pop-up menu and choose Blue shirt man. If you have Available in these designer colors open as well, you'll also see it because it's also the same physical dimensions. Well, let's go to Blue shirt man here and we want Red and we want the Background layer. These are flat files so background is all you are going to see. Then for Source 2, Living large in Lab that's what we want, we want Background and we want to change it to the b channel.
Right now we are multiplying, which I don't know, it could work if there were no other blend modes on earth, this could service reasonably well. Let's check out a couple of other things. First set it to Normal and this allows you to see the Red channel by itself just so that that we can be reminded of the channels that we have to work with. Setting it to Normal 100% allows us to just see Source 1. If we set things to Normal 0% then we are just going to see Source 2 because we are seeing through Source 1 so this is the b channel right there. All right, so interesting. Let's change Opacity back to 100% and let's try out some other modes.
Like Overlay. Let's go ahead and kind of burn the two channels into each other and that is better than what we saw a moment ago with Multiply. If we wanted a stronger effect, we could go with something like Linear Light but it doesn't work out very well for this image. What we really need is to lighten the effect more than we are seeing here so let's try Screen, the opposite of Multiply. So we are getting a very, very light image and that's interesting but we are losing our darks. Now there's an even lighter mode than Screen called Linear Dodge (Add) and tell you about Add in just a second but if you choose that, it's really going to blow out the colors.
This is actually a good degree of contrast between highlights and shadows but we need to save the shadows to more darken them up and to bring the highlights back into the Normal realm because right now it looks like he has got his face about three inches from the sun. So I want a control that gives me this kind of brightness but it allows me to darken things up and add, notice that Add in parenthesis that's because it's really dRAWing from this guy right there, Add. If you switch to Add, you are going to get exactly the same effect but you are going to get a couple of different options. Offset allows you to brighten or darken the image by a certain amount of luminance level.
So if I start pressing Shift+Down arrow, you are going to notice that we are reducing the brightness of the entire image at this point by 60 luminance Levels. That's still bringing some of the colors back into the visible range because these colors, these whites are so blown out, they are way beyond white. If I kept reducing this value, we could really get those whites down to something more reasonable but if we did that, we would start bringing in too many grays as well. So what I suggest we do is take the Offset value down to -70, let's say.
In that way, we have some decent blacks, we got some good whites, we have a few midtones in between them that we can rub them out pretty easily. But here, I just want you to see this. This is a difference just so you know we've made some progress. This is a difference between just having the Red channel which was as close as we were with the single channel. Notice the difference between that and Add according to our current setting. So we are really getting rid of a lot of those bright colors especially in the background. We are brightening up this section of the color but that's okay. It's worth to hit, and now I'm going to click OK in order to accept that modification.
So this is going to become our base, I'll go ahead and rename this channel right here, base. It's going to be the base for mask. We are going to actually turn that into a mask, we are going to elevate the contrast with the Levels command and then do a little bit of brush work, you'll see it's very quick and easy. We are going to be doing all that in the next exercise.
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