Monochrome backdrop — typically blue or green — for digital keying. Replaced post-production with background plates. Brightness and saturation are critical.
You stand in front of a bright blue or green surface, the cinematographer shoots, and later you're in a completely different environment — that's bluescreen, and it only works if you understand the physics behind it. The color isn't decoration; it's a tool. Blue became the standard because it's rarely present in skin tones, and most cameras produce less noise in the blue channel than in the green. Green has its place when higher resolution is needed or when blue appears in the scene itself for dramatic reasons.
On set, it's all about even lighting — that's the point many underestimate. Spots, shadows, peeling paint at the edges: all of it will cost you hours in post-production. The screen must be at least as bright as the foreground subject, ideally brighter. I work with a light meter and spectrometer, not just my eyes. The saturation must be constant, otherwise, you'll get fringing and transparent areas in the keying process where there shouldn't be any. The size of the screen is pragmatic — bigger is better, but not all productions have space for a 10x6 meter area. More intimate scenes can also be done with smaller panels, as long as the background behind the subject remains completely saturated.
The distance between the talent and the screen is underestimated in its importance. Too close, and you'll get color spill on hair and clothing — the blue or green contaminates the foreground edge, and the keying becomes chaotic. I maintain a distance of at least 1.5 to 2 meters. The camera position, in turn, determines how much screen you need: a wide shot requires more height and width than a close-up.
In editing — and this is where I see many mistakes — the screen isn't just composited out. You need mattes, refinements, color correction. The keying tool (Premiere, DaVinci, After Effects) extracts the blue color mathematically, but true professionals build in layers: luma keys, chroma keys, isolated mattes for difficult areas like hair. Spill suppression is the next level — systematically removing blue excess at the edges without damaging the subject. The best bluescreen shot can be ruined in post if the post-production isn't clean.