Chroma Keying: A Special Effects Staple

Written by Mark Trinkle

     The words Chroma Key Compositing may not sound familiar, but the concept is one that has been around in the film industry for more than half a century. It is more commonly known as using a green screen, and it's almost impossible to have seen digital media in this day and age and not to have come across something involving Chroma Key technology in one form or another.      
     Big budget movies have used something similar to the modern day Chroma Keying since Lawrence Butler created a traveling matte process

(the analog equivalent of digital Chroma Keying) involving a blue screen to create the visual effect of a genie escaping from a bottle in The Thief of Bagdad (Korda, 1940) (Bialik, Kristen. "Keyed Out, Colored In: Chroma Chromatic Dreams."). But now in the age where so much technology is in the hands of everyday people, anyone can use Chroma Key technology whether it be professional studios, professional 'Youtubers' or the even more amateur Chroma keying Green Screen Apps that exist on Itunes or Google Play.
     If you have no experience with Chroma Keying or green screen, you might ask, "Why green?" Well the answer is, it doesn't have to be. For the purposes of Chroma Keying there are green screens, blue screens, and even some orange screens. The way that Chroma Keying works is by focusing on a certain color in the image and replacing every part with that hue with another image that you want to superimpose, whether it be a pre-filmed background or a digital weather map. Therefore it is important that the background color contrasts with human skin color so that your subject doesn't fade or become part of the background (Risson, Kylie. “What is Chroma Key?”). It is also important for the subject to not wear anything with the same color of the screen you are using, otherwise they run the risk of being like Brick in Anchorman 2 (McKay, 2013) wondering where their legs are (“The Chroma Key Effect."). There are some situations where the costume needs to be a certain color and so green is not always ideal. The first Spider-man (Raimi, 2002) film is the a perfect example of this because both Spiderman's blue costume and the Green Goblin's green costume had to be those colors and as a result the action scenes had to be split up with each character filmed in front of the opposite color screen to avoid ruining the shot. But for the most part green is the color of choice because digital cameras capture more details in green with less light. ("5 Elements of a Great Chroma Key.")
     So you have the right kind of screen, what else do you need? The most important thing to keep in mind in order to set up a good shot for Chroma Keying is lighting. The key is having the screen evenly lit (which is sometimes hard to tell with the untrained eye) while also having the subject far enough away from the background that they don't cast shadows. If the subject and background are well-lit there are a lot of various softwares that can do Chroma Keying ranging from iMovie to Adobe AfterEffects, with the amount of control and specificity ranging based of course on the quality of the software. ("The Chroma Key Effect.")
     Despite being a one-of-a-kind process that is a staple in modern Special Effects for Hollywood and beyond, Chroma Key technology has made its way to the masses and can now be used by anyone and everyone which opens up endless possibilities for both film and media.

Risson, Kylie. "What Is Chroma Key?" Lumeo. N.p., n.d. Web. 18 Feb. 2015. "
The Chroma Key Effect." Creating a Title Paint-On Effect With RED. N.p., n.d. Web. 20 Feb. 2015.
Bialik, Kristen. "Keyed Out, Colored In: Chroma Chromatic Dreams." The Huffington Post. TheHuffingtonPost.com, n.d. Web. 20 Feb. 2015.
"5 Elements of a Great Chroma Key." FilmmakerIQcom. N.p., n.d. Web. 20 Feb. 2015.

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