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Prerequisites of a Good Keying

Please note that this is a BETA version of the document. All information presented is correct but we are working on improving the details.

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When setting up green screens for virtual production by far the most important thing is to properly prepare the background. If the background is not well prepared you cannot have a perfect result, even if the keying process in the software is set up properly.
This article lists all the necessary elements of preparing the background before production.
The main objective, when preparing the background is to make it appear as homogeneous as possible. The uniformness of the background should not change even when the talent moves between the studio lights set up for illuminating the talent (talent lights) and the background.

Preparing the background

Depending on the material used as background, there are different issues to look out for, but in general, these are the following:

  • Check if the background has any visible imperfections and fix them if it has.
  • Avoid creases in the material.
  • The background should not have any holes, tears, or ruptures.
  • Make sure the background is clean and that there are no dirt spots on it.
  • The background should disperse the light as much as possible and have no reflections or shiny parts

Preparing the lighting

Aximmetry's keyer was designed to work best with a homogenous background. To achieve a clean result, good lighting is a must.

Background lights

The aim of the background studio lights is to light the green background as evenly as possible. Generally speaking, the more even the background is lit, the clearer the final keying will be. Illumination of both the talent and the background should be homogeneous and major casted shadows on the background with high contrast should be avoided.

Talent lights

When you are setting up the lighting for your presenter (with the talent lights), you should keep in mind how it would affect the lighting of the background. Moving or talent-tracking spotlights is considered a bad idea since in most green screen setups they would ruin the balance of the background lighting.

You should also consider matching the lights of the virtual studio to the real studio, so the talent will look more like part of the virtual scene. This way you can achieve more realistic virtual setups.
Think about the environment into which you are compositing your subject. For example, if they are being composited into a night scene, it does not make sense to have them brightly lit, because they won’t fit into the scene.

Example of a good lighting setup

Example of a bad lighting setup

As you can see in the image below, the lighting of the background is far from even. The left side is way more bright than the right side of the Green Screen.

Camera Settings

We strongly recommend turning off auto exposure in your camera.

It may seem counterintuitive, but when shooting a green screen, you want to saturate the screen—in other words, darker is better. There are a few reasons for this. One is that a well-saturated screen provides good color separation, while a bright screen can be harder to key. The rule of thumb is to have your screen be ¾ of a stop darker than your key light. In addition to pulling a better key, a darker screen will project less reflection, also known as spill, onto your subject. This spill can contaminate your foreground subject, making it more difficult to pull a matte/key with clean edges.

Preparing the objects and the talent

Dressing the talent in darker colors is preferable since it shows high contrast compared to the background. High contrast helps the software to differentiate between the talent and the background. Green (or the color of the background) and colors that can reflect green (like white), should not be worn.  Reflective accessories, such as jewellery tend to be a bad idea. They reflect a high amount of green, which leads to holes in the final image.

The same idea can be applied to objects, such as chairs, tables, or bottles. Green objects will be cut out with the background, and reflective parts (like chrome-plated legs) can result in holes in the final composite.

Positioning the talent and objects of interest

You want to keep your subject as far away from the screen as possible. This way, the talent can be better lit without the lights affecting the background, and the distance also keeps the reflection of the green background off the talent, which will result in better keying.

Continue to Keying

Once you finished preparing your Green Screen, you can move on to the Keying:


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