How Curves Work: Input and Output
now that we got a basic understanding of how images work, what are Gov is? Um, we're gonna talk about actually what the curves adjustment layer is in, how we can use it to color corrector images. Um, the curves adjustment layer are curves in general is a curve that it's, ah, tool that allows you to remap the tones found in your image. You can select the tone and either make it darker or brighter. Change the RGB value and in turn, the curbs helps all the other tones that are beside it get a just that accordingly. So that's really what's happening. When you create a curves adjustment layer, you create a point you can click and drag to adjust that. But we're not just the just thing that point. We're also adjusting all the other values that are right next to us. What that curve is doing. We're adjusting all the other values accordingly. The best way of thinking about curves is input and output. If I click and drag that point out, we have a straight line. A straight line means that there is...
no change in the curve. If I just, um, click on the curb, you'll notice that I have an input of 1 28 And by clicking on it actually adjusted the image just a tiny bit. The output is 1 25 If I change it to 1 28 Now we have an input of 1 28 in an output of 1 28 So I haven't made any changes. But if I want to make that particular value darker, I can either drag it up or use the up arrow keys on the keyboard. Go up. So now, actually, I accidentally hit the wrong thing here, so let me just go back to 1 28 So originally I was at 1 28 Now I'm at 1 67 Dragging up makes the image brighter. Dragging down makes the image starker. But again, we're always talking about values. The original value is the input and the output is the value that becomes after you adjust it. So when you're working with curves yet again, I'm gonna create another curves adjustment layer. When you're working with curves, you have two points by default. You have the black point which is down here in the bottom, in the white point right here on top in that point determines what the darkest point of the images and what the brightest point of the images. So if you look at your history, Graham, which is this graph here that displays where the data is in the image and you see this great in here going from black to white, you'll notice that the darkest values are right about here. It's a dark gray. It's not really black. This is why the image looks a little watched out because the darkest value is sort of a dark grey in the brightest, value is a light grade, so we really don't have white or we really don't have black. If we wanted to create some contrast, weaken simply click and drag the black point over to the right, right about where we start seeing some data on the hissed a gram. We can do the same thing with the white point, click and drag them one to the left and notice now how we have some contrast in the image. So again we're remapping the tones in the image so that we can adjust it accordingly. Also, here's a little shortcut key for you guys have You hold, option or alter the PC and you click on one of these points the image turns white. If I'm on the black point and if I drag to the right, you'll start seeing some colors once I see black, that means that that is the darkest point of that image of the darkest point of this images. Like right about read about this. This area here, the same thing is true for the white point. I can hold option click in this case, it turns black. But if I keep dragging to the left, you'll start seeing where the information starts appearing. So the brightest point is right there, right where it turns blue right here on this wave. So you have that option if you need to, um, and you can always come back and edit it. As I just said, another way of thinking about the curves adjustment layer is as a dimmer switch like you may have at home. If you're at home and you want to turn the light, you may have a dimmer switch weaken, pushing them or switch up you at light. You drag it down, you subtract light so the room becomes darker. So that's essentially what the curves adjustment layer is doing with the points. So if I have a point here, click and drag up image groups. Let me make sure that this is enabled. Here you go. Have a point. Click and drag up. Dimmer switch goes up in which gets brighter. Click and drag down image. Get starter. So now we're going to start talking about some things a little more complicated. But I created this graphic here so that we could understand how that how this works. Um, we talked about clicking and dragging the dimmer switch upto at light and dragging it down. So subtract light. That's what happens in the RGB composite when you have old three R g v uhm channels being adjusted at the same time. So if I click on channels on the channels panel, I can click and drag that out and actually let me make these Icahn's larger so that you could see so those are larger icons now. So if I click and drag up, actually, let me make sure I'm in the is disabled there. We don't let me enable it. So if I click and drag up. You will see that all the channels are getting brighter at the same time. If I click and drag down, you'll see that all the channels get darker at the same time. So that's what the R G V drop down is doing here. It's adjusting all three channels at the same time, but you can adjust each individual channel accordingly. So let me just reset the curve, go into the Red Channel, and now I can click and drag up on the Red Channel and on Lee. Their red channels adjusted. So let me bring this back here and I'm gonna reset the curve. Now, what this graphic is telling us is that when you drag above the center line on the Red Channel, you're gonna get the light of that particular channel. So we're gonna get red. So I'm gonna select the Red Channel, click and drag up. We're gonna get red light. But if we go below that center line now, we're reducing light in that color and introducing the opposite color in this guy's case, I n. So I'm gonna go back into the drop down select green. You can drag up we have green drag down, we get magenta. So you're stunned that you're starting to see that relationship in the tools that we're working with. Blue. You drag up above that center line and you get blue. You drag below, you get yellow. I sort of which Adobe would apply that overlay onto that panel and 11 of the reasons I'm glad they haven't done it because it gives me a job. But, um, if they did, I'll be very helpful for people struggling with curves to actually do something very something similar to what I just mentioned in the color balance. The color values that adjustment layer has that relationship displayed on there on the slider so they could do something similar for curves. I don't know why they haven't done it, but it's there in in the ah color balance adjustment layer. And you can use that as a reference to see what the relationship is between each color. Okay, so we're gonna end this section just by talking about a couple keyboard shortcuts. I'm a really big fan of keyboard shortcuts. I think that you should learn the ones that are most useful for your workflow um, specifically talking about curves. It's a couple shortcuts that I like using, which is, um, when you click on the curves, um, the properties panel here you create a point, obviously, and you can create more than one point. You can actually create a total of 16 point points where you can have a total of 16 points. There. There's two. By default, you can have 14 total. You're probably never gonna have more than four, um, unless you're doing something extremely complex. But I have never used more than I think. Five is probably most interviews, but you have an ability to create up to 16 points in the curved, and when you create points, you can adjust them by using the up and down arrow keys on a keyboard or the left and right arrows. And usually that's what I prefer doing because sometimes just simply by creating a point, you accidentally make an adjustment like there was click on it and notice that the input is 1 20 in the output is 1 27 So I actually went up seven values just by clicking on it just because of the motion of my hand so usually what I like doing this once I do that from there, I can readjust that and just use the up and down arrows and then hold shift. If I want to go up faster or down faster, you can also, when you have multiple points again, if you're working on something, have multiple points to select the point. You can click on it, but again, usually by clicking on something, you might make a small adjustment that you don't intend on doing so I recommend using the, um plus in minus keys on the keyboard to go up and down the curb. So let me show you what that means. You see how this filled in square. That means that that's selected the one with the outline. It's not so if I want to go down the curve, I can hit the negative key on the keyboard right next to the zero and it goes down. Or if I want to go up, I can hit the plus key. So we have those keyboard shortcuts to help us navigate through the curve much more easier. And there's more keyboard shortcuts for the curves adjustment layer. These are the ones that I figured would be the most beneficial. Um, one of the things that I do want to mention is that if you wanna just speed up your workflow a little bit, you can hit command em to bring up the curves, adjustment our them, start to bring up the curves adjustment, not the layer to bring this up here. So image adjustment curbs, that's what command and dust. But if you want to work with adjustment layers, Photoshopped gives you the ability to remap keyboard shortcuts so they can do what you want. So you can go into edit keyboard shortcuts, and you can go into layer and let me scroll down and find that here. There's an adjustment layer section here. New adjustment layer right there curves. There it is command and okay, so should work. So if I accepted there we go. So Command M now brings up the new adjustment layer window here. I could rename it, give it a color, give it a blending mode, change the opacity and press OK, and that creates a curves adjustment layer instead of going into image adjustment curves. So that could be a useful keyboard shortcut for you. or you could use the icon here and just select curves every time totally up to you. But I just wanted to give you that option in case you like using keyboard shortcuts, and you can take a advantage of a keyboard shortcut that's already built in for curbs, but that probably isn't very beneficial for you.