So now let's move on and look at other adjustments that are much more powerful than Levels. Levels is very useful, but I think there is something that can be dramatically more useful. And that is, as I work my way down this adjustment menu, I get beyond Levels and I find Curves. Curves is the ultimate tonal adjustment. It can do things that no other adjustment can do, and in fact the other adjustments we used thus far are actually using Curves behind the scenes to do the work that they do, and they're just trying to present you with the simpler screen, a simpler interface to interact with. But if you want full control, you want to use Curves. Now Curves is something that is not easy to learn on your own, but I'll get you to understand how it works and it will take you practice before you are good with it. But the practice I think is worth it, because you will get ultimate control over your images. So in Curves, let's see how this works. Well if you look at Curves it's a diagonal line g...
oing across a grid. And at the bottom is a gradient that has all the brightness levels you can have in your picture. And in fact most of the time this gradient will be reversed, where black will be on the left. It's only because I have a grayscale picture that it's reversed. If I take this image and convert it to RGB the vast majority of images we're going to work on will be RGB and therefore if I go into Curves after that now you see black is on the left. Whereas a moment ago it was reversed. Why is that? Well when you're working with grayscale it's thinking about ink, and when you're working in RGB it's thinking about light. The two are opposite of each other. 100% light is the same as 0% ink. And therefore it flips it. It'll make sense in a few moments. So we have that gradient at the bottom then the diagonal line is just telling you how much light would be used to create the shades you see down here. So to create black, this is all the way at the bottom because you would use no light whatsoever. To create something this bright if you go straight up you'd use this much light compared to the amount you could use, which is all the way to the top. And as you work your way this way you see the curve above, that diagonal line, that is, gets higher and higher to indicate you'd use more and more and more light. And once you get to white the curve is all the way to the top because you've maxed it out. You can't get any brighter than white so you can't go any higher than that. So this would be as high as you could possibly go. The way I think of it, is since you're talking about light I think about a dimmer switch. If you go to your kitchen and you find that one of your lights is on a dimmer and it's not the kind that's a knob, instead it's the kind you push up and down it's just like Curves. If you move that dimmer all the way to the bottom it turns the lights off and the room is solid black, you can't see a thing unless there's windows. Then as you move the slider up you add more light and it gets brighter and once you max out that slider as high as it can go it's not possible to make the room any brighter without adding some other light source. And in the case of Photoshop, the brightest we can get is white so moving it all the way to the top is white. So just think of it as picking one of these shades and going straight up until you hit the diagonal line and that tells you how far up the dimmer switch would be. You're not as high as you could possibly go because it's not white. You're not having lights turned off, you're somewhere in between. All right. Then, what can I do with this? Well, you can move your mouse onto your image and if you click this little hand icon that's on the lower left then that means that if I move my mouse over my image, it should think about curves. And so when I go over my image you'll see a circle in Curves and the only thing that circle is doing is it's telling me how much light is in the various areas I put my mouse on top of. So if you were to go straight down from wherever that circle is appearing and you look at that bar that spans the bottom it would be sitting directly above the exact shade my mouse is on. So it's just telling me how much light is in each area. All this doesn't sound too exciting yet, well what if I want to make two of these bars exactly the same brightness level, but I want to leave all the other bars alone. I can do that. If I want to take this bar and I want to take this bar, and get them to be the exact same brightness level, I can do it very quickly and easily in Curves. And I can take the other bars and get them back to where they used to be. This is close to that. If you know what you're doing. And I haven't described enough yet for you to know what you're doing. But let me turn Preview off, here's before here's after. Do you see those two bars that became identical? It looks like the brightest part of the image is getting a little too dark so I have to adjust that too. But let's then say instead I want to do the opposite. I want just those two bars to look more dramatically different to each other than they used to. Well, let's start over here and I want to make this bar brighter. I'm going to turn on this little hand and make this bar brighter and this bar darker. So there is a greater difference between the two. I can easily do that. Then I want the other bars to go a little bit back to where they were not exactly, but closer. I have control over that kind of stuff. And I have none of that control when I'm in Levels or Brightness and Contrast. I can't click on my picture and say "think about this brightness level" and do something specific only to that brightness level.