First, you need to decide on a green background material, Paper, Textile or Paint ?
Your choice will depend on a number of factors for the scene, however, all the above mentioned options designed for this purpose work well, as they are manufactured to provide the high luminance values and color saturation for keying effects, specifically produced for the digital video system.
Next you need to light your Green Screen. Generally, what you’re after is a large, diffused, light source that will wash over the screen evenly.
Frequently used light sources are 2 x Lowell Tota Lights, some people also use the Tota Light with umbrellas as reflectors, which offer a softer light or 2 x Red Heads, but it can be difficult to get that smooth even light.
There are a few fixtures you could use, but one of the best options is Kino Flo. The amount of fixtures required to light the screen will vary, depending on the size of the screen being used.
For a small screen size say, up to 2.5×2.5m (8x8ft), you will need typically 2 fixtures to light the screen, placed facing the screen on either side. Two x 2 bank or two x 4 bank fixtures, depending on the type of lights you use from the Kino’s range and the strength of your lights used on the talent or foreground.
Why use Kino Flo ? What you pay for in a Kinoflo fixture is the ballast…the power supply. A Kinoflo ballast is consistent, flexible and has a high cycle rate (meaning you will never see it flicker), even when the quality of the power source is unpredictable. Kino Flo also offer a great range of lighting control tools, such as Honeycomb louvers, Bat Wings etc.
Apart from Green screen use, the Kino will also be great for other projects, where a soft, even light & low heat output is required.
In the Kino fixture, you can use a choice of Kino Flo manufactured True Match lamps, available in 2900k, 3200k 5500k colour temperatures, as well as green & blue spiked lamps, specifically designed for Chroma Key applications.
To illuminate the green screen, you can use either daylight 5500k or indoor 3200k lamps, however, using a green light, offers a result of a very, very pure green that is easier to key.
For best results using Green spiked lamps, you need to have proper separation of the subject and the screen, generally we suggest to have 3 or more meters between subject and screen and separate lighting for the subject. The separation of the subject from the backing greatly reduces Green Spill (green light wrap) because less light from above and below are striking the shoulders and legs from various angles.
(In the edit suite, the methods of removing green spill was previously difficult, making this technique of using green light less usable. With editing programs such as Final Cut Pro, Adobe Premier or Avid Express you can obtain some good results, some people also use Plugins such as Red Giant’s Primatte or Boris Continum in conjunction with these programs, which offer great results, especially with fine detail such as hair & de-spilling is much less of a problem than a few years ago).
The separate lighting of the subject, eliminates subject shadows on the backing and allows you to balance the lighting for both the subject and the screen independent of each other.
Light the subject as you would for the given scene. For a typical small screen 2.5×2.5m (8x8ft), simple setup you might have your 2 fixtures for screen illumination (Green) & for your talent 1 x Key Light, 1 x Fill & 1 x Back Light fixtures using either 5500k or 3200K lamps depending on the scene.
How you light your subject is up to you. One thing that is important, however, is to make sure that both your foreground and green screen are well lit.