Green screen setup without a studio
Chroma key removes a background by color, and it works exactly as well as the backdrop is even. For keying out a person, a few dollars of green fabric or card with two even lights outperforms any monitor, because a screen behind a person is too small and casts green light onto them.
The short version
- Hang the green behind, not against. Fabric or card, pulled flat. Keep the subject a couple of steps in front of it so shadows fall out of frame and green light does not bounce onto shoulders.
- Light the backdrop evenly, on its own. Two soft lights aimed at the green from either side, separate from any light on the subject. Even is everything; bright is optional.
- Light the subject separately. A key light on the person, placed as for any portrait. Keeping subject and backdrop lighting independent is what makes the edge clean.
- Lock exposure and key. Auto-exposure drifts and the key drifts with it. Lock the camera, then let the software pick the green from the backdrop itself.
Chroma key is a simple contract: show the software one color it can trust, and it will remove that color wherever it appears. Everything about a good setup serves that single sentence. The backdrop must be one color, evenly lit, and nowhere on the subject. Get those three things and a bedsheet keys like a broadcast; miss them and no purchase fixes it.
Why green, specifically
The choice is engineering, not tradition. A camera sensor's mosaic samples green at twice the density of red or blue, because that is where human vision is sharpest, so the green channel arrives cleaner and less noisy than any other, and a key pulled from it holds finer detail at the edges: hair, fingers, glass. Meanwhile skin of every tone carries very little green, so the algorithm separating person from backdrop is rarely forced to choose between them.
Blue is the classic alternative on the same reasoning with the weights shuffled, and earns its keep when the subject must wear green.
The fabric-versus-monitor question
A color site should be honest here: if you need a green screen for a person, buy fabric. A monitor showing perfect green has two unfixable problems as a human backdrop. It is small, and a backdrop must overfill the frame with margin to spare. And it is a light source, so it sprays green onto the back of the subject, which the keyer then dutifully turns transparent: glowing edges, vanishing shoulders.
A few dollars of chroma green fabric or card, pulled flat, does not emit anything and comes in any size. Where the screen earns its place is at small scale and in testing: keying an object on a desk, checking what your software does with a perfectly uniform field, or picking the exact green your pipeline likes best from the color library.
Lighting is the actual work
Even lighting on the backdrop matters more than the backdrop. Every wrinkle is a micro-shadow, every shadow is a second shade of green, and every second shade forces the key threshold wider until it starts eating the subject. So: fabric pulled taut, two soft lights raking it evenly from either side, and the subject standing far enough forward that their own shadow falls to the floor instead of the green, and the green's bounce falls short of their shoulders.
Light the person separately, as for any portrait, and lock the camera's exposure and white balance before recording, because a key tuned against auto-exposure is a key that drifts. The whole recipe is separation: backdrop from subject, backdrop light from subject light, and the camera's opinion from the passing clouds.