Use Curves to Remove Color Cast
[Instructor] - So we're gonna work with one of my favorite photos ever, not only because I love food trucks. For those of you who have lived in the Bay Area, you know how awesome food trucks are. I don't know if you guys have a lot of 'em here. Yeah, you do? All right, great. I love this photo, not because it's great, I love it because it sucks and it's great for this thing I'm about to show you. So I like using the Curves adjustment layer, and actually I think I made that too fast, so let me show you how I created that. I can click on this icon here, and then go into curves, and now I have a curves adjustment layer. The curves adjustment layer allows you to change the luminance values of the photo by dragging on points that you create on that curve. But you don't need to know any of that because Adobe, our good friends at Adobe, made that button right there. It says auto, right? You guys ready to see the magic happen? Ready? Awesome, right? (laughs) No, it's terrible. I don't know why...
Adobe, Adobe has, I believe, four different algorithms that are applied to the auto curves adjustment layer, and by default it's that one. I, personally, don't like it, but there's a way that you can change the different algorithms. Now, I don't know why Adobe likes to hide things, but they hide stuff in Photoshop. If you hold the Option key, or the Alt key on the Mac, and click on auto, you get the auto color correction options. So, once again, that was Alt, Option on the Mac, auto color correction options. By default, enhance, brightness, and contrast are selected as the default algorithm. And you can see the result there. And you can click through the different algorithms and see which one works better for you. In my opinion, the best algorithm to use is find dark and light colors. So watch what happens when I click on that algorithm. Ah, much better. You can also click on snap neutral mid-tones, and it makes it just a little bit better, like so. Now, that's the algorithm that I wanna use by default all the time, 'cause I don't wanna have to do this every single time. So you can click on save as default, so that checkbox there. So I'll click on that checkbox, press okay. So now, next time I create a curves adjustment layer, I can simply click on auto and it applies that effect right away. Now, usually I love auto features, but I don't like just showing auto features without explaining what they're really doing behind the scenes. Because, to be frank with you, that algorithm, that auto feature, doesn't work 100% of the time. So when it doesn't work, you need to know how it's working behind the scenes so that you can adjust it and then make it work. So who here has been using Photoshop for like more than 10 years? One person, a couple people. All right, so those of you that have been using Photoshop for a long time, you may or may not know this old color-balancing technique. So when I first started using Photoshop, in Photoshop I was taught how to remove color casts from photos like this, and the way I was taught was by going into the curves adjustment layer, clicking on the RGB, the channels red, green, and blue, and then making adjustments to these. And the adjustments are actually quite simple. You would go into the red channel first. You would look at the histogram. This is the information of how much red light we have in the image. And you would need to make sure that the black point, this little point here, is next to the peak of information. This one, the white point, is not. The peak of information starts here. So I would click and drag that one to the left. By the way, if you are working at home and you don't see the histogram, let me show you how to bring that up. You can click on the fly-out menu, select curve display options, and you can check histogram. So in case you don't see that. Curves, display options in the fly-out menu. The fly-out menu are these little line icons that you see on every panel. So there's menus hidden in there. And, again, Adobe hides the good stuff in those panels. So always click on 'em and see what you find. But, anyway, so now I can click and drag my white point to where the information starts. Also, just to show you another tip, 'cause this is a tricks and tips class, if you hold Alt, Option on the Mac, when you're clicking on these handles, they turn black. And notice that when I get to this point, I start seeing some red. The reason you're seeing red is because this is the red channel. So this is where the information starts. So even if you didn't have the histogram, you can just hold Alt, Option on the Mac. And notice that when the information starts on the histogram, that's also where we start seeing red. So you can do that as well. I like using the histogram better 'cause it, to me, it's much easier, but you can use either or. Anyway, so I need to do that for all the channels. Red. The information for white starts here. The information for black starts here. Now go into the blue channel and do the same. So what did we do there? We found the dark and light colors. That was the name of the algorithm. So that's basically what the algorithm was doing. Then, at one point, I asked you to click on that checkbox that said neutralize grays or whatever it said. I can click on this eye dropper here, which is the gray point, and just click on anything that should be a neutral gray. The side of the food truck was an off white. If I click on that, it neutralizes the gray. So that's basically what the algorithm is doing behind the scenes. It's doing all this work. Now, sometimes you may get to a point where you make your adjustment, and I'll do it really quickly again. Actually, I'll do the auto version this time, and I'll just remove that center point. So that center point there was the mid-tone, and I'm just gonna remove it just to show you what could happen. So sometimes you may get to this point and there may still be a, you hit the auto button, there's an adjustment. It almost works, but not really. The key is using that eye dropper, that gray point eye dropper, just click on anything that should be a neutral gray and it'll push it into something that works. In this case, the auto button did a really good job without the eye dropper, but that's what you would do in case the auto button didn't work, use that gray eye dropper. And some of you may be thinking well, why don't I just use the eye dropper from the beginning? And when I click on this icon here, which resets that layer, the adjustment layer, this little circle thing, that icon there resets the layer back to default. I have the eye dropper selected. If I just click on the truck, it neutralizes the grays, but we didn't find the light and dark colors. So that's why it looks washed out still. So sort of a two-step process. Hopefully the auto button can take care of it. If not, you can do the eye dropper and then it'll work. I hope that last part made sense.