Unlock your inner Steven Spielberg. Add some Hollywood type production techniques to your next home video project. Use green screen or chroma keying to add new dimensions to your production. Green screening is one of the oldest special effects tricks used by Hollywood and television. Everyone is familiar with it, but may not be aware that is the technique being used. You have all watched the weatherman stand in front of an area map and point to the temperatures and clouds, haven’t you? You have also watched movies where the heroine jumps over moving vehicles and flies through the air, right? These are chroma key or green screen effects. Basically, they film the subject in front of a green screen, then they overlay that footage against a fake background.
This technique is popular with both still and video photographers. The process of removing a subject from one video or still photograph and superimposing it on to another may seem complicated but actually it is not. Here are a few simple steps to help you get started.
Setting up your studio may be the most complicated procedure of all. You need a certain amount of space and specific equipment. For lighting, I like to use construction halogen work lights and bounce them off of large white surfaces. I generally use two work lights and purchase two large white poster boards from Wal-mart to use as my light reflectors. Next for the green backdrop I purchase four yards of light green material. I also construct a frame of PVC pipe that I can use to support my green screen material on. This is an important step; you want the green screen to be as tight as possible and wrinkle free. The wrinkles can cast shadows and prevent a clean composite transfer when it is time to overlay the video footage.
Lighting the screen involves positioning the lights so that your talent does not cast any shadows on the screen. When you are ready to begin recording their performance they should be positioned about 4 feet in front of the background. You want the background to be lit as evenly as possible. Cross lighting from the sides of the green screen is the preferable technique. Place one light reflector unit on the upper left side so that it cast its reflection across the top of the green screen at a downward angle and the other light reflector unit on the lower right side of the green screen so its reflection is cast along the bottom of the screen at an upward angle. This will take some experimenting and editing demonstration tries with your video editing software to determine which lighting arrangement composites’ the best.
Now it is time to begin shooting your video. First, you should shoot your background video footage. You can use existing video clips and still digital photo images if you wish. It is very important that you be familiar with the background elements so when you shoot your green screen footage you know where to correctly place your talent so they will appear natural when combined with the background. When done selecting or shooting the background footage, shoot your talent’s portion of the production. Remember their placement is important. Also remember to allow your green screen material to cover the floor, especially if you’re doing a full body shot. Additional lighting focused on the talent is preferable as it will aid in the composite step.
The final part of the process is the combining of the clips. How to do this varies depending on the video editing software that you are using. You will have to work with two video tracks to do this. One will contain the green screen footage and the other will contain the background footage. Your video editing software should be equipped with a chroma key plugin. You use this plugin to remove the green screen background. This is referred to as compositing.
Basically you take the green screen footage and run it through the chroma key filter. Is will ask which color you would like to make transparent. You select the green color and it erases the green background from that video track, leaving only your talent’s action. You then simply merge the background video track with the composite green screen video track and you have your talent performing their actions against the background you selected.
Wasn’t that easy? It was a little labor intensive but still easy, yeah? With practice it will become a piece of cake and your capabilities will also increase. Image what you can do once you have mastered this process. Steven Spielberg…Watch Out!
Resource: Personal Experience