Neutralizing a color cast
Neutralizing a color cast
In this exercise, we're going go ahead and correct for the color cast of the image, which in my opinion is too pink. We're going to do that by applying some Curve modifications on a Channel by Channel basis. Now, we're not going to go as nuts as we went with the Composite Curve here, because that ends up just getting thoroughly confusing in my opinion; at least I get confused by it. So we're going to apply a fairly simple curve modification, as you'll see. Anyway, if you're working along with me, I still have open-- this is not a catch-up document. It's just the original High-contrast elephant.jpg image.
What you would do, if you just want to catch up right now, because I want to show you this other thing, I want to show you how to work with presets, and what you would do is you go ahead create a new Curves adjustment layer; you know how to do that. You just go here to the Adjustments palette, and you go ahead and click on this guy right there to add a new Curves adjustment layer. Why don't I do it with you, so that we're doing it together, what the heck? So I'll go ahead and throw that one away. Here is my original elephant. I'll go here, add Curves. Actually, you know want I'm going do, I'm going to Alt+Click or Option+Click on that icon right there, and I'll call it elephant correction or something like that, and then click OK.
Then notice I have got my flat curve once again. I don't want to sit there and add all those points; we had like eight points in that curve just a moment ago, I'm going to go up to the palette menu and I'm going to choose Load Curves Preset; I invite you to do the same. Then you would burrow your way into the 13_levels_Curves folder, that's inside of your exercise files folder, presumably on your desktop or some place, and then get this guy, Reduce contrast.acv. This will be your points that will load into the graph as soon as you click on the Load button. There they are, just like that.
Notice this Reduce contrast item now appears as a preset up here at the top of the Adjustments palette, and you can see that you've got all these other presets you can choose from. Photoshop CS4 shifts with a ton of color correction presets you should know, for all kinds of different commands. Some of them are fairly useful. I'm not sure that you're going to be applying any of them on a regular basis. What's more useful in my opinion is just to know that you have them there and that you can use them for your own purposes. You can create your own presets that you can use over and over again, like Reduce contrast right there. You can switch between, you could say, hey, there is Increase Contrast, wow, does that not work for this elephant? There is Color Negative, ha, ha, ha, not really what we're looking for, but, hey, it looks about as good as the original did.
Then we can come back to Reduce contrast and go oh, that's better. So how do we compensate for the color cast? Well, I'll tell you, here is what we're going to do. I want you to switch to the Red Channel; and I'm going to do it from the keyboard, because I'm really struggling by the way to come to terms with these new keyboard shortcuts in Photoshop CS4 for switching between channels, it's just, I got to get this down. I'm really having problems. I'm so used to the old 1, 2, 3 for Red, Green, Blue and now it's 3, 4, 5, which doesn't make any darn sense. But anyway, it's Alt+3 for Red; that's Option+3 on the Mac, there it is.
I'm going to click right there in the center to set a point at 128, 128, and then I'm going to press Shift+Down Arrow three times to reduce that Output Level to 98. So we're mapping what was formerly 128 to 98. That means we're really taking the red out of this elephant and there goes the pink. So that's taking the pink out of the elephant. That's good. Now, we want to maybe add a little bit of color to the grass. I'm going to add a little bit of blue and a little bit of green. So let's go ahead and press Alt+4 or Option+4 on the Mac to get green. By all means, if any of you come up with a way of remembering these darn things that I can convey to other people, that would awesome. I haven't come up with anything, but I haven't really tried, I have to say.
Anyway, click in the middle. I did it, you did it too, if you want to. Press Shift+Up Arrow to raise the Output Level to 138. So we're going from 128 to 138. Then Alt+5 or Option+5 on the Mac to go the Blue Channel. Click in the center again. Gosh, I'm good at clicking in the center, and then press Shift+Up Arrow twice to change the Output Level to 148, and we have ourselves a beautiful pachyderm here, to give you a sense of the difference. Actually, the first thing I'm going to do is I'm going to press Alt+2 or Option+2 on the Mac to return to the RGB composite, and I just want you to see, isn't that awesome seeing all of those Curves on top of each other there? So you should see the black composite curve, which is pretty complicated, and then this simpler red, green, and blue Curves. Then that gray thing in the middle is just showing you the mean, the original diagonal line. You can just see where everything ultimately came from.
Incidentally, if you don't like seeing that great diagonal line in the middle there or you don't like seeing anything; you actually have a lot of control over what you see inside of this palette, you can go up to the Adjustments palette menu right there, and you can choose this command, Curve Display Options. Then you can, for example, turn off Baseline, that will turn off that gray line right in the middle. Did you see it go away? You can change the number of intersecting grid lines there by clicking on that little guy, if you want to, or you can click on this to set it back to the way it was. You can turn off the Histogram, if you like. I wouldn't do that. I'd keep the Histogram on. Channel Overlays is something you can turn off too. See all the stuff. Intersection Line by the way, I'll go ahead and show you what that is.
I'll click OK. Intersection Line is this line that you get when you're moving a point around, like that. See those lines, the vertical and horizontal lines that are going off to the sides there. All right. Let's undo that modification though. I don't want that. One other thing; this is completely out of context, but you can change the number of grid lines just by Alt- Clicking inside the graph, that's an Option+Click in the Mac. Isn't that weird? So you can just do that one on the fly if you want to. That is old school Photoshop I have to tell you. Anyway, I want to show you one more thing. Let's go ahead and load the preset from disk that goes ahead and creates the color cast compensation. It's the exact same correction that I have already applied here, but I want to show you the different between the two.
So let's go up to the palette menu, choose Load Curves Preset. I'm going to grab this guy right here, Pachyderm protection, and click Load, and this is this Channel by Channel modification that I have applied. Just so you can see the difference between them. This is without the Channel by Channel modification. See how pink she is. Now, you can see, yeah, she is pretty darn pink. She is pretty in pink, but she is pretty darn pink. She shouldn't be that pink, and she should be like this instead. That looks more elephantine to me. Just so you can see how far we've come with this image in general, this is the before version of the image, which has a startling level of contrast, and sort of has a certain effects quality to it that you might actually like for some sort of image, but this color compensation that I have applied there, this adjustment layer, if I turn it back on, that's a more naturalistic elephant, I think. A better effect all the way around, thanks to the power of Curves here in Photoshop.
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