Why are Green Screens Green?

Technology in film and television has greatly developed over the decades, with CGI (computer-generated imagery), and other computer graphics. An important element to computer graphics are green screens, which is a background in front of which moving cast members are filmed, and a separately filmed background can be added to the final image.

But why are green screens the colour green? Would green screens work if they were any other colour? We try to understand an element that is used in many cinematic and television productions today by answering the question: why are green screens green?

Are green screens always green?

Well, no. Basically, green screens can be gray, white, black or purple, but they are most often blue and green, because these two colours stand out the best. When the screen is filmed, the colour needs to be picked up very clearly so that it can be replaced with a different image.

If the person being filmed in the shot was wearing a purple tie with a purple screen, the purple would be picked up and disappear as well. In the film, weather and gaming industry, green and blue screens are used.

How do green screens work?

So what exactly happens when green screen technology is used? The technology is called chroma-keying. A specific color is chosen, and replaced by a different color or background. On the weather, a green coloured background will be replaced with background of the weather map.

Sometimes blue screens are used instead of green screens, because the colour is softer than in a green screen. However, many people like to wear blue clothes, and much fewer people wear blue with bright green. Not only do people like to wear blue on screen, making blue screens less functional, but also, green screens have the highest luminance out of all the colour channels.

“Green spill”

Because they are bright, sometimes there is also reflection from green screens, which causes “green spill”. Green spill occurs when there is too much light reflection, making it so that some colours reflect onto the subject. If you look closely, sometimes you will see a faint green coloration around the contour of the person on screen. To avoid “green spills”, you need to watch your lighting before shooting.

Green or Blue?

In the end, the colour of the background screen will be decided based on what the colour of the foreground objects are. If the objects in the foreground are going to be green, then the best bet is to opt for a blue screen!

Conclusion

In the end, the answer is pretty clear: green screens are most often green because green is a bright colour that can be picked up easily, and it’s rare that objects and people wear a bright green colour.

Did you know that the green and blue screen method was actually developed in the 1930s? It was at RKO Radio Pictures that it was first developed. The first film that used the process was The Thief of Bagdad in 1940.

Related: What is Movie Snow Made of? 

Video: Green Screen Ghost Prank

This is hilarious and definitely worth a watch!