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One of the more fun features you'll find in iMovie '11 is its ability to superimpose one clip over another using a green or blue screen effect. To accomplish this effect, one of your clips has to include a green or blue background. iMovie can automatically remove the green or blue parts of the scene, letting you see through those parts of the footage to the footage from the clip underneath it. For this exercise, I am going to import some footage from my exercise files. So I'll choose File > Import > Movies, and I've copied onto my Desktop a folder called green screen, which contains these three movies.
I am going to create a new event, and I'll just call it Green Screen and import them. And yes, I do want to import the entire directory. Okay, so here is my footage right here. So to accomplish the effect, you have to be shooting in front of a green or blue background, and it has to be one of those two colors and not any other color. The brighter and more saturated the green or blue, the better. And even though you can buy green and blue screen paints and backdrops, there is no need to spend a lot of money or to get all fancy. To create this example, I just went to a local hardware store and bought a can of bright green, non-glossy paint and painted a wall on my office.
In these shots, I am just standing under regular fluorescent ceiling lights to show you that iMovie can still do a great job, even if the green background isn't the best or even the most evenly lit it could be. You just have to make sure your subject isn't wearing any green and then none of the objects that you want to remain on screen have any green in them; otherwise they'll end up being see- through along with the background. Or if you are using blue, make sure there is no other blue in the shot other than your background. Now before you can apply the green screen effect, you should first go to iMovie > Preferences, and under the General section, just make sure Show Advanced Tools is checked.
If it's not checked, you won't see the Green or Blue Screen options. Okay, let's see how we do this. I am going to create a new project. File > New Project. Again, I will just use no theme. I'll call this Green Screen, Widescreen, and I know that this was shot at 30 frames per second, so I'll select that and I click Create. Okay, so here is my new blank project. So I am first going to drag in the background clip that I want to use, which is in this case is just these trees. So I'll just select that entire clip, drag it in, and now I'll drag in the footage of myself in front of the green screen.
Again, I'll select the entire thing, drag it on top of my clip, like so, and you can see now we have all these options open and we saw some of these in the earlier part of the chapter. In this case, because I have a green screen, I'll choose green. Now if you have a blue screen, obviously, you will choose blue screen. That's really all there is to it. iMovie removes the green parts of the clip, and all that remains are the non-green parts, which happened to be me in this case. Let's see what this looks like. (video playing) (Garrick: Ah, the great outdoors.) There it is. Now there's no way to fade in the Green Screen effect, so you should probably line up the beginning of the green screen clip to the beginning of the clip underneath it; otherwise, it will look like your green screen subject suddenly pops into the shot.
Let me exaggerate that a little for you. It will look like this. And suddenly I just appear. Now if that's the effect you are going for, all the better, but if not, drag the green screen clip to the beginning of the background clip. (video playing) (Garrick: Ah, the great outdoors.) Now, there are in actuality many other things to put into consideration to make your green screen effect look more realistic, including properly lighting your subject, so it looks more like the two scenes are actually one scene lit by the same light source, and making sure your camera angles match, so it doesn't look like you're looking down on your scene while looking up at your subject.
But as far as parts of the process that iMovie takes care of, that's almost all there is to it. Now I say almost because there are a couple of other things you can do to fine-tune your Green or Blue Screen effect. For example, if your green screen background isn't quite being completely subtracted by iMovie--maybe you're seeing some shadows bleeding through--you can help iMovie learn exactly what it needs to delete as long as the last frame of your green screen shot is just of the green background itself. So if we look at this clip in the event browser, after I walk off at the end, we have only the green background. So, if iMovie is having trouble with my shade of green, I can click the Action menu for this clip, choose Clip Adjustments, and then here under Background, I can choose Subtract last frame.
This helps iMovie better determine exactly what it's supposed to remove from the clip. But again, this only works if the last frame of your clip is of just the background. Now iMovie also allows you to manually crap out unwanted portions of your green screen clip. Down in this clip in my Event Browser, I am standing in front of the wall again, but one of my studio lights is in the shot. Let me go ahead and delete this clip and I'll select this one, drag it on, make a green screen. So when I play it, it's pretty much doing exactly what it's supposed to do, and now I see myself and the light in the shot.
But I really don't want that light in the shot. So I am going to select the Green Screen clip, and over here in the Viewer, I am going to click Cropped. Now I can drag this frame that you see here around the portion of the shadow I want to keep. Anything outside the cropped area will be removed from the shot. So, for example, I can drag this corner here and I'll drag this corner here, like so and you can see it pretty much eliminates the light. But you do need to be careful that you don't crop the area so tight that it crops up parts of the subject that might move outside that area.
So if I leave this, say, tightly cropped to where I'm standing right now and play it, you can see I kind of walk off the frame there, and I sort of just disappear into another dimension. So what I probably want to do here is drag these corners all the way to the edges of the frame, like so. That way I will be able to see myself in my entirety as I walk off the screen. In fact, you kind of see the top part was cut out there a little bit, so let's raise that up, like so. Let me see how that looks.
So you can see even though that light was clearly in the shot, it's no longer visible because we cropped it out, and there I go walking off the screen. So that's the Green Screen effect, and remember that iMovie also comes with a variety of backgrounds, which you will find by going to the Maps and Backgrounds button. And these are great if you are creating a video report or blog and you just don't have anything interesting to stand in front of. Just film yourself in front of the green or blue background and then you can drag in one of these clips to act as your background. As we have seen before, some of these backgrounds are animated, while others are not. I'll grab that one, grab my footage here.
Let me get a green screen, and you can see what that looks like. (video playing) And if you change your mind about the background, you can easily just drag another one on top of it to replace it. You can even put a green background back there if you wanted to, which probably defeats your purpose and is a little redundant, but there you go. Anyway, give that a shot. There is really no end to the fun stuff you can do with the Green and Blue Screen effect here in iMovie.
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