Part Eight - Green Screen Principles 2

1. Location or studio. – Ideally record your green screen shoot in a dedicated studio. A studio will normally have black walls and ceiling to suppress any spill light from lamps. Ideally don’t have a room with white walls or ceiling, as they can reflect back onto the subject, causing potential keying problems later.

2. Find a long room. Your studio or room needs to be longer than you might imagine. You need to create a distance between the screen and the subject to reduce the effects of the green light spilling back onto the subject.

3. Discuss and understand the shoot before the actual shoot day. It is vital for everyone to understand what the background and the foreground action will look like before the shoot day. The background can affect the direction of the lighting, the framing of the shot, camera operating and more. People do not appreciate unforeseen surprises, and a storyboard will show how the subject will appear over the background video.

4. Colours. You need to make sure your subject and branding colours are suitable before the day of your shoot. Don’t wear green clothes. (or blue if you are using a blue screen background). Perhaps this is obvious, perhaps not. Green screen works by eliminating green from the picture and putting another image in its place. If you wear the same colour as the screen you will appear invisible.

5. Choose a suitable camera. – Not all cameras capture the image and record the colour in the scene in the same way. Cameras have different ways of recording the picture, and they collect and record colour in different ways for the same colour information. The more colour information your camera collects and records means you will capture more information, and this will help your options in post production. A low end camera will not capture the range of colours, so it will be harder to eliminate the subtleties of green later around the subject matter.

6. Use a large screen. - A bigger colour screen means you have more flexibility in shots. As you will need to create some distance between the subject and the screen, your screen needs to be quite large due to the angles involved. Make sure it is wider than it is high, as the video camera works in that aspect ratio.

7. Choose between Green screen and Blue screen. This may not be as obvious as it sounds. If you are planning to place your subject in a scene in the daytime you will need to record their performance against a green background. In a daytime shot any spill on the subject will potentially be disguised due to the background of trees and grass, perhaps. In a night shot the inherent colour is blue, so green spill would potentially show up more. If you shoot a night scene against a blue screen the blue will be masked by the inherent perceived blue colour of night and moonlight.

8. Light your background screen separately. This is crucial. Make sure you have the flexibility to keep the light hitting your subject totally separate from your green screen lighting. Your software works best when the green is evenly illuminated and uniformly the same colour. Most large studios have the green screen background and the cinematographer will also light the green screen with additional green light. If there are any shadows on the back screen at least they will be green.

9. Keep the lighting on the screen as even as possible. If you have lamps too close to the screen it can cause "hot spots" (some areas lit brighter than others), and can then alter the saturation and colour of the background. This in turn can create difficulties later in post production. Ideally have a monitor with a waveform monitor built in, and check the exposure accurately this way.

10. Lighting choice – As your green screen needs to be lit very evenly, you will normally need several lamps around the screen. If you have a small room the heat output can be intense. LED or fluorescent lighting can be a lot cooler, softer and more diffuse and the spectrum can sometimes be tuned to light the green screen. Halogen lighting (or tungsten lighting) can become hot and it is also a warmer colour, so may not be as accurate colour rendering for green screen.

Look out for more articles on green screen here

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Posted on August 5, 2015 .