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Whether you create a garbage mask at the beginning of the process or after the process of keying is really up to you. I personally like to get everything cut out of the scene that I'm not dealing with so I know exactly what's left to use for my key. If you're unfamiliar with the term garbage mask, all it is the process of creating a mask to cut out any extemporaneous elements that you don't want in your scene. So if we look at our video clip here, let's select Layer 1 and turn the visibility off.
You can see I have a graphic background that I want my talent over and I have two shades of green. This is basically the edge of the stage. Now if we scroll out, you can see there's a slight black line all the way around this as well. So we're going to create a mask that just goes around her making sure to cut this element out and this black line out. All right, so let's scroll back up here and I'm actually going to choose Fit up to 100% just so I can see all of the edges of my comp. Okay, now if you go up to the Tool panel, let's click and hold, we can just choose the Rectangle tool.
You could choose the Pen tool if you want to manually click around, but I like to start wide and then work my way in. So with the Rectangle tool, make sure you have Layer 1 selected, and let's click in the upper left-hand corner and drag down to the lower right. Now we don't want to go this far because we want to cut out that light green area, the edge of the stage, and there we go! We've created our garbage mask. Now some people would call this finished, but what I would do is scrub through the timeline with your current-time indicator and make sure that the talent doesn't move outside the edges of your mask.
There is nothing worse than having your talent move outside the edge and their shoulders cut off, or something like that. One of the things I like to do is actually bring my mask in a little bit so I have less to deal with in the process of keying. Even though this is a beautiful flat, evenly-lit key, it's kind of fun to just pinch in the edges a little bit. So let's select our mask on Layer 1 just by clicking on Mask 1 and go up to our Pen tool in the Tool panel. If you hover over one of the lines with the Pen tool, you will get the Plus symbol.
So just click on one of the edges here, I'm going to pinch this in right about neck height. So here let's click here, and we'll do the same thing on the right side, let's just click there. Okay, now I'm going to grab my Selection tool, and if you Shift+Click the four top points here just by holding down Shift and clicking, we'll have all four points selected. The reason I'm doing this, sometimes it's easier to just use transform controls to move your points. Obviously, we could click on the points and move them in side by side, but with the points selected, if you press Command+T or Ctrl+T on the PC, you can then click on one of the edges and start to drag in.
Now as I drag in, on the Mac, I'm going to hold Command; on the PC it would be Ctrl, and just sort of pinch the edges in a little bit. Now when it's set the way you like, you can press Return or Enter on your keyboard. I'm just going to slide these over to the right a little bit since the angles of her shoulders are set up this way. Now when I press Enter, I have my garbage mask, and again, it's really important to scrub through the scene and make sure she doesn't go off the edges of the mask. And now as I'm looking at this, I realize, yes, we have the edges in, but remember there is that black line all the way around the scene? If we move our mouse over the canvas and scroll out here, you can see it a little more clearly.
So let's click on the lower right corner of the mask and then Shift+Click on the lower left and we can just click and drag this up just to crop this one edge off. Now with our mask actually set, let's deselect the mask for a quick second and now we can select our talent and actually just move her and the mask slightly down off the scene. Now when we key this, we'll go ahead and position her properly within the scene, but I just want to start by moving her just a little bit off the edge of the canvas.
So in summary with garbage masks, you want to make sure that you don't crop in on your talent and have them get cut off in a funny place, but also you want to make sure to cut out any extemporaneous elements that you won't need in your scene.
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