1.4 Removing Color Cast

[SOUND] Hello everybody. Welcome back to using curves in Adobe Photoshop. In this lesson, we'll talk about using the curves adjustment to remove the color cast of an image. Let's start with this image. It's very well done, but it does have a severe color cast to it that may not necessarily be clearly apparent to you in looking at it like this. But let's add a curves adjustment layer, and talk about some of the ways we can use these other features within this curves panel. Primarily, I wanna focus on the eye droppers, that are over here on the left side of the panel. You'll see a set of three of them. One that looks like it's filled with black ink, one that looks like it's filled with grey ink, And one that looks like it's filled with white ink. These are ways of setting the white, black, and mid tone points of an image, and these are extremely helpful, and very handy tools. I like to start by setting the white point first. So you grab the eye dropper that has the white ink in it. And you click on the pixel in the image that you think should be 100% white. And then, looking through this image, I think over here in the right, where the sun is beaming through this window, that should be 100% white. Likewise, we click on the black eye dropper. And try to find a pixel that we think should be 100% black. So I'm going to say deep within the shadows of the shelf should be the very darkest points of this image. So we'll click right in there. And that's already going a long way to changing the color cast of this image. But next we're going to set the gray points. So we'll use the gray eyedropper. This one can be a little bit more difficult in that it's hard to know exactly what in this image should be a midtone gray. It may take a couple of tries to get a good result. This instrument up here on the shelf that looks gray should be a midtone gray. If you don't like that, you can always reclick and sample again and continue sampling until you get a result that you like. And I really like the way that one turned out. Now, if we toggle off the curves adjustment panel, we can see what the original image looked like, and you can tell that really did have a severe colorization to it, that we may not have noticed immediately. But when we contrast it to the corrected image, it's clear how much color distortion was there. Now let's take another look at the curve's panel and see what's going on in here. Our regular curve is still this straight line, but behind it, you can see there's three different colored lines. Those represent the different colored channels of the image. It's an rgb image so it's the red, the green, and the blue. So what these eye droppers are doing are making intentional adjustments to these color channels to help remove those color casts. Now, technically, that could be done manually within each of these color channels by adjusting these color curves, but it's a lot easier and a lot more intuitive to do it using the eye dropper tools.