I bet you have seen weather forecasts in the TV. Most of the times, the presenter is standing beside a large map, and the map/weather changes as he/she speaks about the weather condition in different regions. If you are wondering how the animation is done, it is achieved with a green screen (or blue screen/chroma key) effect. What’s best, you can also use it for your next video production.
Green screen (also known as Chroma key) is a commonly used technique for compositing two images or frames together in which a color (in this case, the green background) from one image is removed (or made transparent), revealing another image behind it. In Apple’s iMovie, this feature is readily available for your usage.
The main reason for using iMovie is because every new Mac has it, which makes it essentially free (save for a few cents for poster board, but we’ll get into that later) for all Mac users. Secondly, iMovie is easy to use and is effective for producing top-notch videos.
Keep in mind though, the green screening feature is only available in iMovie ’09. ’08 won’t do the trick. If you don’t have the newest version of iLife, don’t bother trying. All new Mac’s come with this though, so if you aren’t sure, open your version of iMovie and go to iMovie -> About in the menu bar to see which version you’re using.
Enabling Green Screening in iMovie
When I first started using the green screen function in iMovie, I was super confused because as much as I looked, and as confident I was that I was doing everything right, I couldn’t find green screen in the menu! There’s a simple solution to this problem, and I’m going to save you a ton of time here by cluing you in. Before doing anything, go to iMovie -> Preferences, and place a check beside “Show Advanced Tools“. This will make the cool options like green screening, picture-in-picture, and cutaways available. While they are labeled as advanced tools, they’re really easy to use. I’ll show you!
Steps to Creating Your Video
Now that you’ve enabled green screening, the first thing you need to do is decide on what background you want to use for your video. This can be a video or a still image, depending on what the purpose of your video is.
Next, open iMovie, create a new Project, and drag it into the Project section at the top left corner of the screen. To adjust the length of the background to match the movie you want on the background, click the gear in the lower left-hand corner of the clip and select Clip Adjustments, then change the time appropriately.
Now you’ll need to film yourself to add on to the background. First, you’ll need a green screen. This is much easier than you may think. While you can go all out and either buy a fabric green screen or paint a wall green, you can also create one for almost nothing out of green poster board. Just scotch tape it onto a wall, and bingo, you’ve got a perfect, wrinkle-free green screen. Now, capture video of yourself doing whatever it is you want right into iMovie, by clicking the camera button on the left side.
Once you’ve recorded your clip, drag it up onto the background, and when you release the mouse button and the menu comes up, click Green Screen. Your recording will now be superimposed onto your selected background!
Sometimes lighting can be tricky, but when working with lighting, remember these keys: you want the lighting even, and you want it bright. Unless you’re doing this for professional reasons, you can basically use any generic lamps you’ve got lying around the house. iMovie happens to be pretty great implementing green screen tech, and the Mac’s built in iSight is generally pretty capable, so you shouldn’t have too many issues. This is a generally accepted way to light a subject when recording for green screen:
If you do run into any shadowing problems, one trick I’ve learned that can work is to put a light behind the screen. This will help to bring some of the shadowing down in intensity, if it exists at all.
I told you it wasn’t too complicated! Have any questions? Let me know below and I’ll do my best to answer them. What do you plan on using the green screen technique for? Any tricks or tips for other users for those who have done it before?