Uniform green backdrop for digital chroma-key compositing — actor shot against solid color, background added in post. Industry standard because green sits furthest from skin tones.
You set up your camera in front of a uniformly lit green surface — this is the basic situation you'll work with when it comes to digital keying. The actor stands in front of this wall, is lit, and later in the edit, this exact green surface will be replaced by a different background. This only works because the compositing software can isolate the green channel and use it as a mask. Green is chosen because it occurs least in human skin — red and blue are more anchored in the face and body. If you choose blue, you'll ruin blue eyes. If you choose something else, you'll lose detail in hair or edges.
On set, you need absolute uniformity. This sounds simple, but it's the most common source of errors. Folds in the screen, shadows from the actor themselves, varying lighting intensity across the surface — all of this creates fringing, color blotches, and rough edges later on. I always light the green screen separately from the cameras and the talent, usually with large, diffuse sources. A distance of one to two meters between the actor and the screen is standard, so their shadow doesn't land on the green surface. The further away, the better for keying — but the larger the screen surface needs to be.
In practice, you distinguish between the physical material — stretched canvas, painted wall, plastic roll-up — and the later processing. Some productions still use old fabric screens, which wobble and become wrinkled. Modern sets work with rigid, precisely calibrated panels. The camera settings play a role: the shallower your depth of field, the blurrier the screen surface behind the talent becomes — this is desired because blurry edges are easier to key later. Stop down the aperture by one stop, and the compositing work becomes significantly more complex.
The light on the screen must be comparable in warmth and coolness. If you set your key light too hot, the actor will appear unnatural later if the background is cool. Many mistakes are not made during shooting, but because color grading and compositing were not coordinated. The green itself is a digital construct — DCI standard is around RGB (0, 255, 0), but which shade of green keys best depends on your camera, your lights, and your compositing software. Always test beforehand.
News
Live-keying hardware like Blackmagic Ultimatte 12 enables real-time green screen compositing for streaming and broadcast. The systems process chroma keys directly during recording, without a post-production pipeline. Dedicated hardware solutions are preferred over software keying, especially for news studios and live events.