Lighting for Green Screen on Location
More than ever people are shooting for digital compositing with green screen backgrounds. And nowadays much of it is being done away from the controls of a studio setting.

For the unfamiliar, Green Screen lighting implies that your setup will be used in chroma-key production. Chroma-key technology allows the user to select a background color (usually green, but blue is also common) and to drop that color out of the picture, replacing it with other imagery. The most common
use is in TV news sets where a person standing in front of a green wall in the studio will appear to be standing in front of a moving weather map.

The techniques to light for Green Screen on location are not much different from what's required in the studio. Location Green Screens tend to be smaller than in the studio, and subject to the restrictions of the space you are shooting in.

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Setting Up
Our "Studio"
Getting rid of existing room light
Getting rid of existing room light

For our example, we will be creating a green screen shooting set in a typical household garage. The basic technique is a scaled down version of the traditional chroma-key methods popular on the local news, however working on location instead of a set has its own set of adjustments. You must take the extra precaution of controlling ambient light at the location by covering windows and turning off the room lights if necessary. In a practical setting, windows and ceiling lights can easily be close enough to have an influence on what you are trying achieve.

Blocking external light leaks
final setup
Final result, a controlled environment

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Basic Technique

It should be noted that the word "key" is used in 2 contexts here. To "key" an image is a part of the electronic chroma-key process (keyer, key - ing). The "Key" light is the main light on a subject in a lighting setup.

While each chroma-keying system has its own tolerances, the general consensus is that the green (or blue) background must be lit as evenly as possible. Wrinkles, if it is a cloth / temporary background, or seams & uneven paint, if it is a hard / permanent background, should be minimized to help reduce keying problems.

The preferred methods involve being able to light the background and the subject separately. If your subject is human and framed waist-up or looser, this can require between six and twelve feet between your subject and the background. With tight framing it may be possible to evenly light the background with just one broad source. Typically two or more lights are used to light the green screen but in this example the light is a single Omni-light, floor-mounted on a Big-foot & Scissor mount, fitted with a 300W lamp and two sheets of diffusion clipped across its barn doors. The diffusion in this case was mostly used to lower the output of the light, not just diffuse it. A sheet of neutral density gel paired with a sheet of diffusion would have had similar results.

This example shows a standard portrait lighting look. The Key light is a Rifa 88 with 1000W lamp and a 40° Egg Crate to trim the light spill away from the green screen. The Fill light is a smaller Rifa 44 with 250W lamp. The Hair light is a Pro-light with 125W lamp and diffusion gel clipped to its barn doors. The Pro is on a boom rig (KS Jr Stand, Grip Clamp, Full Pole, & Lowel Weights) to keep the stand out of the shot. At this close range we wanted the hair light source to be larger than what the gel frame would have allowed, for increased softness. The larger sheet of gel over the barndoors, as you can see, achieves that effect. Ordinarily, a Rifa 44 would be the choice, but the ceiling was too low. It would be in the shot.

green screen support

Note: In some cases, the distance & angle of the floor lamp to the green screen may cause uneven coverage from the bottom to the top of the screen. Also other examples in this lesson, which use lights with umbrellas to light the green screen, may be impractical due to space restrictions.

If you need to light the green screen from above, but lack mounting options, you can create a rig like the one shown by adding Lowel Interlinks and a Full Pole to 2 KS Stands. Then you can use a Tota-clamp to hang a broad-throw Tota-light with diffusion from the center, behind the talent, to evenly light the green screen. You can also hang the hair light source from this rig.
1) Key light,   2) Fill light,   3) Hair light,   4) Green screen light
the result
The Result
Key Light - Rifa 88, 1000W Soft light with 40 degree EggCrate
rifa 44
Fill Light - Rifa 44, 250W Soft light
Hair Light - Pro-light, 125W, focusing
Green Screen Light: Omni-light, 300W, focusing

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