The ultimate guide to Chroma Key and Green Screen

Ever wondered how a news studio looks like in reality – and wanted to play around with the green screen? Try it yourself! Everyone can reproduce green screens and use chroma keying for home-made special effects. Learn the basics.

Virtual news studios are locations where dreams (as well as nightmares) can become on-screen reality: From dinosaurs suddenly walking through the studio to illustrations of rising water levels and other impressive weather effects, TV channels have been using chroma key and green screen increasingly.

Progress in computer animation and live processing of greenscreen setups have made it possible to project any kind of setting into these news studios. Filmmakers rely on the method for most kind of special effect, too – such as the invisible cloak in the Harry Potter films. But there is more good news: Anyone can use chroma keying at home nowadays. Let us walk you through the basics.

The essentials: What is chroma key and how does it work?

Chroma key is a method to replace a predefined color, the so-called key color, in filmed material – and insert (digital) content such as graphs, maps and animations or combine it with material from another shot.

The most common key colors used are green and blue. Why these two colors? They are in opposite contrast to the color of the human skin.

The purpose: Why use chroma key?

Chroma key helps you to combine two different shots in the same frame. It replaces all the pixels with the defined green or blue key color with content from other film material or with digital content. This means: Your imagination is the limit!

Possible settings are:

• Virtual studios for your own “news broadcast”;
• Putting yourself in the most unlikely locations such as the jungle, underwater or the oval office;
• In a more sophisticated way, you also can use the greenscreen environment to insert digital animations.

Blue or green: Which color should I use for chroma key?

Choose your key color according to the colors in your shot: If there is blue in it, use green and vice versa. Plants will partly disappear in greenscreens, as will a person wearing blue trousers in bluescreens. However, be aware of the effects of the colors: Green is twice as reflective as blue, so it tends to contaminate your shot more than blue.

There are rare settings where both colors are needed at the same time – Spiderman with his partly blue costume fighting against a green Goblin is one example you might (or might not) encounter. In this rare case, you will be forced to shoot the protagonists separately.

Why is lighting so important for chroma key?

The greatest challenge while using chroma key is the illumination of your setting. The reason: Your key color must be as homogenous and soft as possible across the entire setting. Take extra care to avoid:

• Shadows: They slightest deviation from the key color will result in errors – and shadows will do exactly that. Solution: Use extra lightings between the objects and people you are filming and the background in key color to avoid shadows.
• Pleats: Make sure your backgrounds are ironed, even and uniform. Pleats will result in fractions of the key color which will subsequently disturb the process of chroma keying.
• Dust and dirt: Studios are like pharmaceutical laboratories – they are super clean. Don’t let some dust put your greenscreen project in danger!

Pro tips: Distance, confidence monitor, camera focus, compression and on-click keys

No more than 3 meters! This is the ideal distance between camera and background in key color. The bigger the distance, the more complex becomes your setting in terms of lighting, focus and color.

Provide a confidence monitor for your protagonists. The greenscreen setting is harder to use for people in front of the camera: They interact with objects that are they cannot see. It may be a bit costly, but if technically possible, a screen can provide live orientation for the people in front of your camera.

Switch to manual focus. If your chroma key setting is well lit, many cameras will get lost in the color. Use your camera skills and focus manually.

Avoid compressed filming at all costs. Compression will result in a deviation of colors which could potentially make your shots useless. RAW is the best option.

All set for the shot? Then start with a still of your key color background – in so doing, you will be able to make one-click keys in post-production.

Bring the power of Green Screen footage & Chroma Key

You can cleverly bring the power of green screen footage to your next project. Whether you’re combining several takes into one composite, adding a colorful backdrop to a headshot, combining several takes, or creating special effects with different assets, powerful and responsive tools help bear your vision to life.

Remember Chroma Key goes hand-in-hand with Green Screen! Get a quick insight with our video example illustrating how to make a chroma key video with VEGAS POST, and learn how to key “green screen” footage like the pros in this step-by-step guide.