Join Deke McClelland for an in-depth discussion in this video Channel-by-channel edits, part of Photoshop CS4 One-on-One: Advanced.
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In this exercise I'm going to show you how to correct an image from the Levels adjustment layer or the Levels dialog box, if we are applying a static color adjustment on a channel by channel basis which is the best way to go if you have some sort of color cast that work inside of you images, we do. In the case of this one which I have now gone ahead and saved as Composite levels.psd. So this is my work so far. We have got a three layer image if you include the Background layer. So we have got Background, which is the original image. We have this Auto Color layer that is currently turned off, we are going to turn it back on in a moment, and we have got this Composite Histogram. So we've made a composite modification which is affecting all of the channels in kind, but that is not going to allow us to correct for any cast.
So I'm just going to go ahead and turn off this Composite Histogram here, which is showing us the original version of the image as it was captured, and now I'm going to turn back on Auto Color, Clip 0.20% and 1.5%, because I want you to see something about this layer. I'm going to ahead and click on it, and by the way notice this art behavior. I have to show this to you, because it is really strange and it may end up causing you some degree of alarm. Notice if you have an inactive layer selected, so I have gone ahead and clicked on this adjustment layer that I turned off, and mean while the adjustment layer below which is on, which is not selected, we are going to see the histogram that belongs to the adjustment layer below, along with the settings that are associated with the active layer, which isn't going to do us any good, by the way. I just can't believe they have done that. But any way, it is something to bare in mind, you've to got to watch which adjustment layer is active when you are working here inside the Adjustment palette, because you can end up doing this thing where you are trying to change the settings, and it's like, wow, nothing is happening, amazing, what's going on here? Well, that's because you are working with a dead layer and it's very possible that- yup, look at that. It actually does change the settings. That's ridiculous. Oh my Gosh! Anyway, go and turn that off, and then click on the right adjustment layer, there we go. So it's just a precaution. I'm not knocking the software. No, no, not me. I'm just saying that that's something to watch out for when you are working inside of this marvelous program.
All right, so here -- of course I love Photoshop, I'm just marking it for a moment here. We've got this Background layer that's active. This is recovery mode people, and I have got this adjustment layer that's now active and turned on, so that's good. And this is accurate, believe it or not. Even though I've got this amazing modification that's been applied, so I'll turn it off for a moment so we can see. There is the original version of the image. There is the modified version of the image. Thanks to this Auto Color combination that I have applied here, and yet if you look at the numerical values, it's as if nothing has changed. Now look at that histogram. Something has been done to that histogram, because it's got a bunch of weird little blades cut into it.
Looks like some kind of crazy comb now, with these little gaps in it. And that's because the histogram has been spread, but it's been spread on a channel by channel basis. Nothing has been done to the composite version of the histogram, which is why all of the values are set to their defaults. However, if you were to switch to a different channel by going up here to this Channel Option and selecting something like Red, Green, or Blue inside of this particular image, because it's an RGB image. Then you would see that work has been done. So there is the unmodified Red histogram with the values assigned to it. So we are saying, anything with a luminance level of 23 or darker is becoming black inside of this one channel. Anything with the luminance level 195 or brighter is becoming white inside of this one channel, and nothing has been done to the midtones at all inside of any of these channels as you will see.
Notice the white points stays 195, where this specific modification is concerned so whatever reason, whatever was going on inside of Photoshop's brain when it applied this Auto Color modification. 195 is always the white point, again, that I want to stress inside of this specific adjustment. Gamma was left 1.0 throughout, but the Black point changes from one channel to the next. You can overwrite that of course. You can change it whatever you want. So the first thing I want you to know is that you've got keyboard shortcuts to switch between these channels, and I also want you to notice how they've changed from the old days. So it used to be to get to the RGB composite you would press Ctrl or Command+~ and now it's Alt or Option+ 2, so that couldn't be more different.
And it's because a lot of keyboard shortcuts have been shifted like Command+~ on the Mac will switch you between active windows, and Command+1 or Ctrl+1 here on the PC will take you to the 100% view. So 1 and ~ are basically taken, so now we are working with 2 through 5, and you may wonder, why don't they switch from Ctrl or Command to Alt or Option, and that's because, if we go to the Channels palette here, you'll notice that Ctrl+2 takes you to the RGB composite, and that would be Command+2 of course on the Mac. Where as Ctrl or Command+3 takes you to the Red Channel, and Ctrl or Command+4 takes you to the Green Channel, and we'll see more of this later. Ctrl or Command+5 takes you to the Blue channel. So I would press Ctrl or Command+2 to go back to the RGB view. So we can't use Ctrl or Command here inside the Adjustments palette, because it's already doing something here inside the Channels Pallet. All right, I'm going to switch back to Layers. So that's why it has gotten mapped to Alt or Option. I hate to belabor this, but I wanted you to know.
If you are working with a static modification inside the Levels dialog box, then you can press either Ctrl or Command 2, 3, 4, and 5, or you press Alt or Option 2, 3, 4, and 5. So you can work either way. Either modify your key words, that is, Ctrl or Alt on a PC or Command and Option on the Mac. So just FYI, more stuff to confuse you. All right, so I'm going to go ahead and switch to red. I sort of feel like it need to backed off in the Red Channel a little bit. In fact, here, this is what we need to do. We don't want to just start racing through the Channels. What you want to do is you want to look at the image, and you want to evaluate it.
And you want to say, okay, what's wrong with the image? What's the color cast? The color cast is yellow. So how are you going to fix yellow color cast. You could subtract yellow, which is a combination of red and green, or you could add the compliment, which is blue. So what this image really needs is brightening up in the blue channel. So let's go to the Blue Channel, either by choosing Blue or pressing Alt or Option+ 5 there, and notice, of course in these brightening, I mean, look at all these highlights that are going unused here.
So the highlights have really start till about middle gray actually inside of this histogram, and yet my white point is away over here. So if I drag my white point closer to the ends of the mountain range, right there, then I'm going to introduce Blue into my image, brightening the Blue Channel. So I'm introducing Blue to the highlights and as a result I'm defeating that yellow and making that yellow color cast go away. Now I have gone too far I think with this modification, so let's back it off a little bit, and we'll take it to like something like, I don't know 160 is looking pretty good. May be even something like -- actually I'll take this down to 145, just so that I have a fairly even value going on. Then I'm going to go over to the gamma value, and I'm going to take that gamma value down, because I feel like the midtones and the image are too bright in general. So I'm going to press Shift down arrow in order to reduce that gamma value, and I took a little blue out of the equation, and reintroduced a little bit of yellow. Did you see the difference? So this is the 1.0 gamma value right there. Look at the image, look at Max's face, how it's a little bit blue. If I take that gamma value down to 0.9 by pressing Shift down arrow, I'll reduced some of the blue, and give him a more naturalistic yellow flavor. Just a little bit of yellow in that skin tone. We don't want to make him jaundiced of course, and then you would go, fool around with the other channels.
Now that you have done that and say, well gosh, at this point I feel like, you know what, I could use a little less green too, because green is the yellow ingredient. So I press Shift down arrow, maybe once, maybe twice to take out some of the green, and in this case I have taken out a sufficient amount of green that I have made the image to red, so then I could go over to the Red Channel, and I could reduce it's Gamma value as well by taking it down to like 0.8. I imagine it will work pretty nicely, and then I'm going to back up the white point just a little bit, so that I take some of the red out of the highlights, and then actually I'll brighten this gamma back up just a little bit. So we've got 0.9 for the gamma and red, and we've got 210 for the white point here inside the Red Channel. 23, which is the way this was set by default in the first place is fine for the black point.
I am not going to adjust the shadows, because they are already in good shape, but you can if you want to. I'm just not going to. All right, and then I could either introduce a little more green like so, in order to yellow up the image a little bit. By taking this white point value down to 190, I'm just playing around here folks in order to see what I feel comfortable with, and then if I was to say gosh, I want more green, I would increase the gamma value like so, and if I wanted less green, I would decrease the gamma value, and that's going to give me more of sort of a red, blue, because the red and blue channels haven't been modified at this point, well, I'm modifying the green channel of course. So that's too far.
I would say something, around what I had is working just fine actually, and then let's go back to the blue channel. So this is the kind of thing you do. Kind of go back and forth between the channels just to get a sense of what's going to look best here. And then I'm going to take this white point value down a little bit further, down to 135 by pressing Shift down arrow there and I actually thing this is looking pretty nice. Now I might say you know what, it's still looking a little bit red in places. And I can go to the red channel and play with that, or I could just decide this is enough monkeying around. Let's see, yes, definitely ooh, actually that's pretty nice. 0.8 for the gamma value, or maybe raise it to 0.85. That's good.
All right, I'm going to go ahead and switch back to the RGB version of the image, and then, I want to stress here, this is the way I tend to work. When I know I have got a color cast associated with the image, I might start with like an Auto Color adjustment here inside of the Levels adjustment layer, the way I did a few exercises ago now, and then I would go to the various individual channels, red, green and blue, before I apply a composite modification and visit them and get the color balance right, and then if necessary back to the Composite view and make a couple of modifications there. So for example, I could say, you know what? I can still ease off of this white point. I could still make the image brighter. But I'm not going to, but I could do that if I wanted to and it could also brighten things up inside the gamma that is bringing the midtones little bit, or I could darken them. I could just take the gamma value down just ever so slightly down to 0.97 for example, in order to darken the image just a little bit.
Now to give you a sense of what we were able to accomplish, this is actually really great thing about the Adjustments palette here. We can now, because we kind of clicked off that adjustment layer and came back to it and made some modifications. I can not take advantage of this little revert option here. This Reset to previous state option, and I can click on it, and I'll see the original Auto Color adjustment right there. This is what this adjustment looked like before we embarked on this exercise, and then if I press Ctrl+Z or Command+Z on the Mac, this is what it looks like.
Now when I go ahead and reinstate my newest modification, so I think this is a heck of an improvement. So this is where we started, and this is where we are now. Very, very nice modification, and just to really give you a sense of what's going on. If I were to turn off this layer by clicking on the eyeball, this is the original version of the images we saw at so many exercises ago, when we first opened it, and this is the I think very successful modification. All right I'm going to go ahead and hide my pallets and zoom in on Max here, so that we can see my boy nice and up close, and personal, and I think very, very nicely modified. Here using channel by channel Levels adjustment in Photoshop.
Recommended prerequisite: Photoshop CS4 One-on-One: Fundamentals.
Download Deke's customized keyboard layouts and color settings for Photoshop under the download feature.
- Using blend modes, adjustment layers, and layer styles
- Organizing a layered composition so it is fluid and editable
- Creating and editing type in Photoshop
- Using blur effectively
- Using adjustment layers to add color
- Combining layers into a clipping mask
- Working with Camera Raw