Tip #2: Uses of Chroma KeyPosted: September 14, 2011
I suppose I should start out by explaining what chroma key is, due to the fact that I tend to get the question quite often. Simply put, chroma key is green screen. Less simply put, chroma key is the act of converting a certain range of colors to transparent. This is most commonly associated with using a green screen to put actors in places that are impossible to access in real life. Blue screens are also becoming very popular in films. However, I think chroma key has much more potential than some people realize. I discovered this myself a few years ago when I was experimenting with using clip art for special effects. Yes, I know, but all I had was Paint and Sony Vegas at that point. But I also know that many other people are probably in the same situation. So these are my tips for people, like me, who don’t have many thousands of dollars to spend on green screen/graphics equipment.
Obviously, you can always set up a traditional green screen and use that to transport your actors to wherever they need to be. If you don’t have a green screen, you can find them online (http://www.tubetape.net/servlet/the-198/5-x-7-5×7/Detail), or a role of green fabric from Wal-Mart works too, as long as it’s a solid color. When you set it up, try to hang it as flat as possible and set up your lighting to create minimal shadows. Wrinkles, shadows, and other discontinuities in the color of the fabric make chroma keying unnecessarily difficult. To see the example to the right in action, watch Dracula.
If you have no means of creating transparent images, chroma key can be a great tool to use for graphics. Simply open your image in paint, color all but the part you want seen in a color not used elsewhere in the picture (meaning if you are keying a green turtle, don’t use green as your chroma key color), and chroma key the color you added in your editing software. In my example, I painted all but the dagger blue in Paint, then chroma keyed the blue out of the image of the dagger in Sony Vegas, then rotated it and added effects to help it blend in with my text. To see this example in use, watch any of the Steele DAGger videos.
Finally, be creative. Chroma key is not limited to just green or blue in the background. I was playing around with this idea and came up with this short clip:
Basically after I had the title come on, I chroma keyed the white on the fan, then faded the title off. This is a simple example of how else the chroma key feature can be used. What can you come up with?