Using Layer Masks to Replace Sky
The other thing I use layer masks for quite frequently is when I need to replace a sky in an image. So here I have a photograph and it's overcast, so the sky is rather boring. And I would like to put this sky in it. So I'll use my move tool in this case, I'll click within this sky image, I'll drag up onto the tab for the other document. And then before I let go of the mouse button, I'll make sure to move my mouse into that image so it's not on the tab, instead it's within the image. And I'll let go, and then I can reposition this and hopefully get it to fill the frame. I'll close the other file 'cause I already have it incorporated into this one. So I'll click this little X on the other tab to get rid of that. And now I'd like to use a layer mask to be able to see the building that was there. Now, I could work this way where the sky is the topmost layer and add a mask to it, or I could reverse the order of my layers and put the image on top. And in this case with only two layers, it do...
esn't really matter. But let's say I wanted to try out five different skies and I want all five of them to be in the same document so when a client shows up, I can just quickly change the eyeball icons in the Layers panel to show them various versions where they have different options for which sky to use. If that was the case, it would probably be better to have the building on top. Because of the building's on top and it was the layer that contained the layer mask, I could just have multiple layers underneath and just turn off or on their eyeballs, and it would determine what shows up behind the building. If, on the other hand, I do it in the order it's currently in, I would put my layer mask on the layer that contains the sky, and if I need to put three or four more skies in the picture and they're gonna be above the building, each one of them would need to have a layer mask attached to prevent it from covering up the building. So I'm gonna change the order of these layers. But when you have a layer called background, I won't be able to drag a layer underneath it, and I won't be able to grab the background and put it on top. The background layer is stuck at the bottom. That is, unless I double-click on it to change its name or I click this lock symbol to unlock it. Now it's a normal layer, and now you can either move it on top or move the other one underneath, however you'd like. At this point, I want to select the background. So maybe I could come up here to the Select menu and see if it would work and just tell it to select the subject. It'd be nice if it knew where everything was. And it looks like it didn't select the right side of the building, so that's not gonna be quite good enough. So instead, I'll come over here. Maybe I'll use the object selection tool. I can hold down the Shift key to say add to the selection we already have, and I'll circle around this area here to indicate what I really want selected. About like that. And it looks like the area, it got the building and it got part of my wife, Karen, but down below her, it's not selected. If you can't tell what's selected, you can type the letter Q, which will turn on Quick Mask mode, and any area covered in red is not selected. So you can see that we have a lot of the building, but the the road and the portion in between the arms and legs there are not. Type Q again to get out of that. I'll then hold down the Shift key to say I wanna add to my selection, and I'll tell it I wanna add this bottom portion, and hopefully the object selection tool will be able to accommodate me. It still wants to not select the one area, so I'm gonna say screw it, I'll do it after it's a layer mask. I'm gonna add a layer mask to this layer by clicking on the layer mask icon. It'll convert my selection so only the areas that are selected will be visible, and therefore that area between the legs and her arms will disappear. Won't look right. But I can always grab my paintbrush tool, and any area where I paint with white is going to become visible. So in this case, I'm just gonna come in here and paint with white right here. I see this, the word stop and the road is broken up, I can see my wife's hand is missing. Well, let's see how it could be, how it could be easier for me to paint, 'cause right now it's hard for me to tell exactly where I needed paint and where I shouldn't. So there's a way to disable a layer mask. I showed you that in a previous image. You hold down the Shift key and you click on the layer mask icon or the layer mask thumbnail in your Layers panel. But now I can't tell what was hidden by the layer mask because it's disabled, so everything's visible. Well, there's a trick. There's a way to make the layer mask show up as an overlay on top of your picture where it looks like Quick Mask mode where you get that red overlay. And the way you do it is on your keyboard right above the Return or Enter key, there's the backslash key. And if I hit backslash, it should make that layer mask be a red overlay. Now on some international keyboards, that might not work, and if it doesn't work. Let me turn it off by hitting backslash again. I don't know of a alternative keyboard shortcut, but I can show you the manual method for doing it. If you have a layer mask attached to a layer and that's the layer that's active, you should be able to switch to the Channels panel. And if you do, you're gonna see that the layer mask is actually a temporary channel showing at the bottom of your Channels panel, and it'll be what's active. And right there you see a hint of that keyboard shortcut. There's the backslash. You just don't need to command backslash. It's just backslash show by itself. But if backslash doesn't work, just click right here to turn on that eyeball, because that's all the backslash is doing is toggling that eyeball. So if the keyboard shortcut doesn't work because you're on a non-English keyboard and they just didn't wire it up, that's how you can get around it. So now I'm gonna paint with white. And I'll click right here. If you wanna draw a straight line, you can hold Shift and click somewhere else, and it'll snap a straight line between the two. I actually got too far up there, though, so I'll choose undo and manually do that. But anyway, to get that overlay, I just work on a layer that contains a layer mask, and I end up hitting the backslash key, and then I can touch up all sorts of things, like here I can see the red is overlapping the building. Red is what's gonna be hidden, so I don't want the edge of the building to be hidden. I'll click down here near the bottom, and here I might try to do a straight line. If you hold Shift and click somewhere else, it'll draw straight line from where you last clicked to where you're clicking now. And so I can probably touch this up as long as I don't go too close to that edge. Maybe look down the other side to make sure that side of the building looks appropriate. I think I see just the tiniest bit of a red overlay there. There's just a little nook right there that is missing. I doubt it would be important when we put a new sky in, but I might as well fix it anyway. I'm going to paint with black. Right now we've been painting with white, and I'm going to hit the letter X, which exchanges my colors. I'm just gonna fill in that little gap, and then I'll hit X to paint with white and get the overspray I just added off of her foot. There we go. Paint with black down here. Touch it up wherever you need to. And so it can be a nice way to double-check that your mask was accurate for the purpose you need. And I'm guessing I might have an issue right at the tip of this. You see how the red is kinda overlapping that. So if I turn off the overlay with backslash, and I enable the mask again by Shift + clicking on the mask to turn it back on, watch the tip of that tower. You see how it's going away. So I'm gonna disable it again by Shift + clicking on the mask, and I'm gonna show it as an overlay again with backslash. So you see how that's useful. Then I'll paint with white and click about there, hold Shift, click about there to make a straight line, same width on the other side. If I need that little, what would you call it, a little spike at the top, I just need a smaller brush. Just be careful. As your brush gets smaller, it gets harder edged, and so if I end up with a tiny brush, to prevent it from being too crisp of an edge, I'm probably gonna need to bring the hardness down here. So I'm just gonna click where that spire or whatever it is would connect, and I'll hold down the Shift key, and I'll go up here the top so it draws a straight line. All right, Command + zero to zoom out, Control + zero on Windows. I'm gonna turn off the red overlay. That was the backslash key. Or if the backslash key didn't work, then I would be coming in here to channels and just turn off the eyeball that's there. It does the exact same thing. Then I'm going to disable, or re-enable, I should say, my layer mask by Shift + clicking on it. And now we have our sky. I can then use the Move Tool and reposition that sky wherever I'd like or try different skies. And we got everything, even the little tip, and they got, there's a lightning rod at the top. So it's nice for sky replacement.