Join Lee Varis for an in-depth discussion in this video Lesson 3: Curves and color images, part of Beyond Skin: Going Deeper with Photoshop CS3.
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So we saw how curves can be used on a black and white image to control tone and contrast. Now we're going to look at a color image and develop a strategy for addressing the color as well as the tone and contrast using curves. So I have an image here and let's start working on a strategy for dealing with what appears to be a kind of cool colorcast here. What I want to do first is find the lightest value in the image and the darkest value in the image and there's a little trick that we can use to do that.
I'm going to call up a Threshold adjustment layer. Click on the little Layer adjustment icon down here at the bottom of the Layers palette and select Threshold. Now I get this Threshold adjustment which turns the image into black and white. Right now, the slider control is right in the middle, but if I move it down towards the left, I'll see everything turns to white except the very darkest area will be the last thing to go.
And it looks like we have a shadow down here in the bushes. If I turn the Preview on and off, we can kind of see, yeah, this dark point is down over here in the bushes. I'm going to hold down the Shift key and place a Color Sampler right in that point. Now I'll go back to my Threshold control here, move the slider to the right this time to find the lightest area in the image. And right before everything goes to black, I'm looking for a white point in the subject which are the people.
And it looks like right here on this woman's shoulder is the lightest value in the image of any importance. So I'll hold down the Shift key here, place another sample point right there. Now I'm done with this, I don't have to use the Threshold command. I'm only using it temporarily, so I'll hit Cancel and it goes away, and now I have two sample points; one right here and one over in the shadows in the bushes, and we can see those numbers up here.
Let's zoom in and look a little bit. Over here the number one point is the shadow value which says right now 14, 12, and 12. It's not balanced. It's pretty close, but ideally I'd like to see 10, 10, 10 there; a neutral black point. And then over here, I see for my number 2 sample point, this is the white point on her shoulder, 201, 223, 247.
Well it's pretty high in blue and ideally, what I'm looking for is 245, 245, 245 and a balanced white point. So let's see how we can achieve that using curves. I'm going to go down and go to my Adjustment Layer icon here and I'm going to select Curves and make a Curves adjustment layer. So here is the Curves Control dialog and I'll start with my white point which is the most unbalanced here.
I see that I'm high in blue, but I'm pretty close to what my maximum value should be there for blue. So I'll start here, select the end point for blue, and I'm just going to nudge that down using the Arrow keys until I get to 245. Now I'll go over to the Green channel and I still have that end point selected, but now I need to clip that. I want to move that point to the left and bring it up to 245.
So I'll start just by pushing it over, I'm looking at those numbers, 238, 241, 243, and now I'll finish it off with the Arrow keys, 244, 245. There's a shortcut for changing from one channel to the other. So I can go Command+1 or Ctrl+1 will give me the Red channel; Command+2 or Ctrl+2 gives me the Green; Command+3 or Ctrl+3 gives me the Blue, and then Command+~ or Ctrl+~ gives me the Composite channel.
I want to go to the Red channel, so I'm going to go Command+1 or Ctrl+1. I'm in the Red channel, my white point here is still selected. I'm going to move that over until I get close to 245 there, and then finish off with the Arrow keys, 242, 243. Here we go, 245, 245, 245. So I've balanced the white point and we've made a significant improvement in the image.
Let's look over at the black point. Well we could do a little improvement here. I'm going to go ahead and select the black point in the Red channel, which now reads 16, and I'm going to move that point over using the Arrow keys until it says 10. So I move it to the right, now it says 10. Let's move on to the Green channel, Command+2 or Ctrl+2 gives me the Green channel. That point is still selected. I'll nudge it over until it says 10.
Let's go to the blue channel, nudge it over until it says 10. Now we have 10, 10, 10 for my black point; 245, 245, 245 for my white point. And let's look at what we've achieved just by setting the black and the white point. So we've improved the contrast and it seems like we've cleaned up the image a little bit. We still have more to go on this, but you can see how powerful it is just to set the black and the white point.
Now we need to start working on the most important color in the image. And what's the most important color of any picture of a person? It's going to be the skin tone. Almost everything else we can accept some variation, but we like to see good skin tone. So next, we're going to look at how we can adjust the skin tone. All right, so let's get back into this. I'll open up the Curves dialog again, and now I want to find out what my skin value is. So I'm going to place a sampler on this woman's cheek here and we need to evaluate skin tone. It's kind of hard to tell how red or yellow, and we know we can see it's kind of definitely high in the Red channel here.
But it's easier to evaluate the skin tone if we look at CMYK numbers, even though we're in RGB, we're going to change the readout, and I do that here by clicking on this little Eyedropper icon and selecting from the dropdown menu. Hang on, here we go, CMYK Color. Okay, so now I get CMYK numbers. And the important thing to look at is the relationship between magenta and yellow, and then secondarily what the value of cyan is.
What we're looking for is magenta and yellow to be close to each other; magenta and yellow should be closer than either one of those is to cyan. But usually we see yellow as a bit higher than magenta, and right now we have the opposite. So we have more magenta than we have yellow and that's giving us a pink skin. It's like sunburned color. So we want to increase the amount of yellow in this image. So we're going to do that by using the opponent color to yellow, which is blue, and the Blue channel is where we're going to find the control over yellow.
So I'm going to take a little blue out and I'm going to place a sampler in the curve by Command+Clicking that color. And that's where the skin color lives in the Blue channel. Now if I take that out, I will increase the amount of yellow. So now I'm getting 63 and 63. So now they're equal, but I'm also making the color a little bit darker, and in fact, what I'd rather do now is make it lighter.
So instead of adding yellow by taking out blue, I'm going to knock back how much magenta is in this mix by adding green. So I'm going to place now--I'm going to go ahead and place a sampler in all three channels, and the trick to doing that is to hold down the Command or Ctrl key and the Shift key and click. And that'll place control point in all three channels. So right now, we're going to add green to knock back the amount of magenta.
So ideally, what I'd like to see is at least 10% more yellow than magenta in this value, and so I'm adding green and I am now in 55, 68--over here. Here we go, 57, 67, that's a pretty good value for the skin tone mix here. And I look over here and I can see that I've taken the red out of the skin. Now ideally, I'd like to see cyan at about a third or up to one quarter slower than the average between magenta and yellow.
And right now it's way up at 45, so that's giving me kind of a dark color for the skin. I'm going to look at the opposite or the opponent color for cyan is red. There's that tone in the Red channel and we'll move that up by adding red, we'll reduce the value of cyan. So I'm going to add red, and you can see 43, it's dropping down, 42. The magenta is changing as well but not as rapidly as the cyan.
I will at some point have to go back and readjust this mix, because now yellow and magenta are changing slightly in the relationship. So I'll go back and go back to the Green channel, add a little bit more green to knock down the additional magenta which just showed up. And I'm going to stop there. This value--this tone is in the shadow side of her face, so I'm not going to really take cyan all the way down because we're starting to look much better now.
Now the last step here, I'm going to go to the Composite channel, the RGB, and make a final little tweak; make it a little brighter, add just a little more contrast through the center, steeping the center part of that curve. And now let's look at the result. We went from dull and blue kind of overcast really somber-looking scene, now we've put a little more life into it. Opened it up; warmed up the colors, all with a curves adjustment.
So you can see by using a Curves adjustment layer, we can target individual colors, very importantly, the skin tone color. Place a point on the curve exactly where that skin tone lives and adjust the color in surgical precision by moving those points up and down. The numbers give us a clue as to which direction to move that point in the curve to achieve the result we're looking for.
Portraiture can be one of the most rewarding skills for a photographer to master, and the right post-processing and enhancement techniques can make all the difference. In Beyond Skin: Going Deeper with Photoshop CS3, Lee Varis uses Photoshop CS3 as a digital darkroom to bring out the best in photos of people, faces, and bodies. He examines tone and contrast, color correction, retouching, and more.
- Customizing the Photoshop CS3 workspace
- Controlling tone and color balance with Curves settings
- Correcting and enriching color with Hue/Saturation
- Converting images to black and white
- Retouching and sharpening portraits
- Enhancing background bokeh
- Adding portrait glow
- Blending luminosity