Green screen effects have been a growing trend in education in the past few districts that I have worked in. Partly because of its ease of use, and partly because it speeds up the process of set design, or eliminates it all together. What is green screen effects? Basically the green screen effect is used to replace a chroma key green background and replace it with another video or still picture. For example, any time you watch the weather report on the news, they are using a green screen effect to broadcast the Doppler Radar behind the weather person. (Just a note: there are also blue screen effects, which is virtually the same thing but uses the color blue in the background instead of green.)
Mac computers come with two programs that you can use green screen effects with pretty easily. Photo Booth has green screen effects backgrounds, although you don’t actually have to have a green screen, but a solid background seems to work the best. To access the green screen effects in Photo Booth launch the application and click on effects on the bottom right of the window. You want to select the second to last square under your shot effects.
You should now see your face via the webcam in the middle “normal” shot and some backgrounds all around you. (Kind of looks like the intro to the Brady Bunch without all of the actors looking at each other within the matrix.)
Now, choose a background and the program will ask you to step out of the picture. This allows the camera to adjust to your background. Again, it is best to have a solid background behind you. Make sure none of you, or any other moving parts are in the camera shot while it renders the background. Once the background appears, step back into the camera and watch how you can now interact with the background behind you.
The other program that allows for green screen techniques is iMovie. This one is a little more complicated to use, but allows you more control with your green screen effects. To access the green, or blue screen options in iMovie, launch the application and click on the word iMovie at the very top of the screen. From this menu, choose Preferences… and select the General tab when the window pops up. You want to make sure that you check the box next to Show Advanced Tools so that you can access green screen effects. Now you are ready to film against a green screen.
For best results when filming against a green screen, you should follow these simple tips;
1. Have a piece of material (paper, cloth, shower curtain, etc.) that is chroma key green in color and has very little wrinkles in it behind your actors.
2. Make sure your actors wear a solid color that is not green, or a hue of yellow, that could fade away when filming. (Having these colors could make the background appear on the actor’s body, which makes the clip look funny. Certain yellows have a ghostly appearance that may work for your clip though depending on what shot you are creating.)
3. Make sure the “mise en scene”, the scene the camera sees, only captures the actors and the green background. That way you won’t have cabinets from your classroom floating above your beach scene when you go to edit your clip.
4. Once you have framed your shot with the camera, keep it as steady as possible. If the camera jiggles it will make it look like their is an earthquake or your actors are in quick sand when you go back to edit your green screen techniques.
5. It’s best to film a little bit of the green screen without the actors for a few seconds before they step into the shot to ensure the best quality. Just like the Photo Booth example.
6. Lighting is key! You may have to play around with this to get the best camera angle and lighting techniques. Good lighting will eliminate the strange fuzzy lines around your actors and objects that make the shot look fake.
7. And lastly, make sure you have a video clip, or still shot that is slightly longer then your shot of the actors in front the green screen when you edit the effect.
Getting backgrounds is a snap. Obviously it would be best to film your very own background to put into your movie, however, some projects require the actors to be in far away lands that is impossible to film. Luckily today we have technologies that can transplant the actors anywhere in a few short clicks. (As a side note, if you are using someone else’s work for your backgrounds, it is always best to get permission first and give credit at the end of your film.)
I will often use Creative Commons to find pictures and/or video clips as my backgrounds for my movies or student projects. This way the publishers of these medias have given permission to freely use their material, but I always give credit where credit is due as well. Firefox has an extension that allows you to download clips from YouTube and other popular movie sites into various movie file formats too.
Now that you have your background clip and your green screen clip, you can layer the two video clips in iMovie using the advanced tools to substitute the green screen. (This cannot be done on the iMovie app for the iPad as it does not allow video layering yet.) This short video tutorial below shows you how to drop the video on top of the background.