What is chroma key? The use of chroma key green screens has become integral to modern filmmaking. Whether alongside the use of chroma key green screens or chroma key blue screens, chroma key effects have become the most commonly used VFX technique in the entire film industry. In this post, we’ll provide a chroma key definition, explain the importance of chroma key technology, and the reasoning behind using different chroma key colors.

Importance of chroma key

First, let’s define chroma key

Chroma key is the term associated with the desired effect achieved from the use of a green or blue screen, or by using chroma key green or blue paint. Chroma key can actually double as both a noun and a verb. We’ll explain what chroma key technology is and how to use it.

CHROMA KEY DEFINITION

What is chroma key technology?

Chroma key technique is the process by which a chroma key color is removed from an image, allowing that portion of the image to be replaced. A chroma key color can be any solid color, most commonly chroma key blue or green. Chroma key can also be used as a verb for the act of removing a solid color from an image. This means that the sentences “I used a chroma key on the video” and “I chroma keyed this video” are both correct. The chroma key technique can also be referred to simply as “keying” or “keying out”.

Chroma key app

How does a chroma key work?

Proper chroma key technique may seem daunting from a distance but it is actually one of the easiest VFX to pull off. The chroma key effect itself being simple does not mean that executing it well doesn’t involve a good amount of technique and craft. A quick and dirty chroma key effect can be pulled off with very little effort, while a cleaner chroma key video takes a little bit more time and care put into the filming and editing but is still relatively easy to pull off well. Using a green screen like a professional is within your grasp. You can execute a chroma key in After Effects, using the chroma key plugin in Premiere, or through the use of chroma key apps. The below video offers an in-depth guide to filming with a chroma key green screen.

The importance of chroma key in green screen basics

You don’t need studio backing or a huge budget to use chroma key software. This is a relatively simple effect that you can pull off single-handedly for free or extremely cheaply, even using a simple chroma key app which will automate the process, but you will find better results when using a full editing program. You can even make your own green screen. The below tutorial shows how to execute a simple chroma key in Premiere.

How to chroma key in Premiere

Or, for a more advanced tutorial, check out the following example using additional elements to execute a chroma key in After Effects.

How to chroma key in After Effects

Executing a chroma key in photoshop is a somewhat different process. Unfortunately, the chroma key workflow is different in every software program, so it may take time to adjust. To learn how to remove chroma key backgrounds in photoshop, check out the below video.

Chroma key out backgrounds in Photoshop

Learning to incorporate green screens and chroma key green paint into your filmmaking toolbox can open up a whole new range of possibilities within your creative projects.

Chroma color

Chroma Key with different colors

There is plenty of room for experimentation in chroma key videos. Achieving the cleanest key possible means avoiding the common chroma key problems. This typically comes down to evenly lighting your screen but there are also some tips and tricks to clean up chroma key problems if your chroma key video has already been shot. Filmmaker IQ shares some tips for using green screens in the video below.

Filmmaker IQ gives tips for avoiding chroma key problems

Green and blue may be the most common chroma colors but they are not the only options. Technically speaking, any solid color can be used as a chroma key background. Red, purple, orange, brown, any solid color at all. The reason why green and blue are used most often is that neither green nor blue is present in human skin tones, and people are the most common subject in shots that are chroma keyed.

Green and blue also have a higher luminosity than other colors, meaning they register more brightly on digital cameras naturally. There are a number of small differences between green and blue screens but for the most part, they can be used interchangeably. The most important thing to keep in mind when choosing which color to use as your key is to avoid overlap with the subjects in your frame that you do not want to remove.

If your subject is wearing a green shirt, use a blue chroma key paint instead of a green unless you want their shirt disappearing along with the background.

UP NEXT

How to Use a Green Screen Like a Pro

Now that you have an understanding of what chroma keying is, you may want to try doing it yourself. Before you jump right into it, be sure to take a look at our step-by-step guide for using a green screen like a professional.

Up Next: How to Use a Green Screen →

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  • Sam Kench is an internationally-awarded screenwriter, independent filmmaker, and film critic. Lover of foreign films; hater of American remakes.

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