Monochromatic backdrop — blue or green — replaced in post with any background. Green dominates because the color naturally avoids skin tones and fabrics.
You need a uniformly lit background that you can replace later – that's where a solid color surface comes into play. Blue screen was the standard for a long time, especially in Hollywood productions of the 1990s. The color blue absorbs less light than other colors and theoretically allows for better separation of foreground and background – at least under studio conditions with precise lighting. But in practice, you quickly notice: blue is everywhere. In eyes, in dark hair, in certain fabrics. The matte becomes susceptible, the fringes ugly, the loss of quality during compositing noticeable.
Green screen is becoming dominant because green naturally occurs in fewer materials. The difference is particularly noticeable in close-ups of faces and in fine hair structures. The green color can be isolated more cleanly without damaging details in the eyes or skin areas. Modern VFX software primarily optimizes its chroma key algorithms for green – that's the reality on set. Nevertheless, blue screen has advantages if your talent is wearing green clothing or if you are working with red hair tones. Then blue becomes cleaner. The decision depends on the specific subject.
When implementing, lighting is everything. A matte-painted wall is not enough. You need homogeneous, diffuse lighting without hotspots. Too harsh light sources create shadows on the screen, which later lead to fringing and ugly transitions during keying. Distances between talent and screen should be at least 1.5 to 2 meters – this avoids spillback, i.e., the reflection of the screen color onto clothing and hair. The camera setting should be in Full HD or higher. The higher the resolution, the cleaner the matte can be generated later.
In editing and compositing (see also Chroma Key), the screen is then subtracted. Professional tools like Nuke or After Effects use intelligent algorithms that don't simply remove all green pixels but preserve the luminance information at the edge. This is the difference between cheap and high-quality green screen work. If you were careless on set – uneven lighting, too close to the screen, incorrect exposure – it can only be salvaged with compromises in post-production.