What is a Mask and How to Use It
The first thing first. Before you begin any type of tutorial with masking or compositing, you want to address how to do it by hand. And I associate doing it by hand very similarly to being a craftsman, because when you're a craftsman, if you do it by hand before utilizing a host of machines and tools, you're able to master something that not many people can do. And there's a few shortcuts and settings that I want to mention, specifically with the brush tool. Now, when it comes to hand-masking, there's a few things I want to mention. And the first thing is we are going to be utilizing the brush. But let's also simultaneously talk about, what is a mask, right? Because this is compositing basics, so if you're watching this class and you're not even sure what a mask is, everyone's writing, good. If you're not sure what a mask is, a mask, first of all, is a way to set the canvas for a selection. So it's gonna say, okay, we have a blank canvas, but with this canvas, we're gonna decide what w...
e're gonna select and not select. It's almost like working on a cousin of a layer. You're not working directly on the layer, you're working on the properties of that layer. So let me show you. Let's say you open an image in Photoshop, alright? Normally, if you try to click on the mask, which is this icon here, it might not work. So what I want you to do is, double-click, or option and click, on the lock. So what that's going to do is change that background layer to a physical layer, and that way, it's not locked, it's not stuck. You know, you can add a mask to it, effortlessly. I'm not sure if previous versions of Photoshop were unable to add a mask directly, because the background was locked, so I mention that, because I want to make sure that everyone's on the same page, and also because, sometimes, if you have a background layer or another layer on top of it, it's gonna work the same now for everybody. So I made sure that that lock is gone. I alt and clicked it, or option and clicked it, and it disappeared. So now, it says layer zero. So, now that we have the layer there, I'm gonna click on my mask option. The mask option is this icon here. It says add layer mask, pretty simple, it's that square with the dot. (laughs) If they left me to name these, they'd be totally different. (all laugh) Click on the square with the dot, okay. Now, the thing with masking is that it works very simply. You have your brush, now you hit the D key on your keyboard to set defaults. Defaults means you have white or black. So this works because, if I have any other color, let's say I've selected like red, hold on a second here, so let's say that I click on my layer, and not the mask, and I select a color like this. What's gonna happen is, if I want this to go black and white again, I'm just gonna hit the D key and it goes to black and white. Okay, if I hit the X key, it flips the colors. So it goes from black, white, black, white. This top color's what we're concerned about. Don't worry about this color behind it, this is the main one right here. So, to work on a mask, you have to, first of all, make sure that you click on the mask itself. Fairly simple, right? So far, you've put a mask, it does nothing yet, and you have your brush, and I'm gonna hit my D key, and set to black and white. I'll select the black color, and by default, you'll have something that's set to a hundred and a hundred. And then we're just gonna start brushing. And if you notice, what happens is, it punches a hole through the image, right? It's cutting it out and showing you a transparency, which is a checkerboard pattern. And we know this is happening, because, if you look over here, you'll see that there's like a black little smudge on the mask layer. So, tip number one, if you want to see what your mask looks like actually, you can click on option or alt and click on the mask thumbnail, and you're able to see what you've masked and not masked. This is so useful because, if you realize that you accidentally masked something and something's not working, you don't know why, look at your mask, because, chances are, you've masked out something and you didn't know it. And this happens a lot, if you're working very subtly on things. You might not notice it. Okay? You can also undo, shift-command-Z, or shift-option-Z, and it goes back multiple steps.