Shooting for the Composite: Seven Checks for Every Green-Screen Day

A good composite is decided on the shooting day, not in the edit. Software has improved enormously, but most of the problems I fix in compositing were created, or could have been prevented, on set. These are the seven things I check every time I direct a green-screen shoot.

1. Light the screen and the subject separately

The screen needs to be even: one flat, consistent value from corner to corner. The subject needs to be lit for the final shot, as if they were already standing in the world you will put them in. Trying to do both with the same lights is how you end up with a flat subject and a patchy screen.

2. Distance kills spill

Every metre between the subject and the screen reduces the green light bouncing back onto skin, hair and clothes. If the studio allows it, aim for at least two to three metres. Spill can be suppressed in post, but it always costs something: colour, detail or time.

3. Match the light direction of the background plate

If the 3D world or background plate has a strong sun from the left, your key light comes from the left. It sounds obvious, and it is the most common reason composites feel wrong even when the edges are perfect. Decide the background before the shoot day, not after.

4. Tracking markers only where the camera moves

If the camera moves, put small tracking markers on the screen: crosses in a contrasting shade of green, spaced so a few are always visible. If the camera is locked off, leave the screen clean. Every marker you add is one more thing to paint out later.

5. Watch your shutter

Fast movement plus a slow shutter means motion blur, and motion blur means semi-transparent edges that are hard to key. For dance and action, I usually shoot with a slightly faster shutter than normal and add motion blur back in compositing, where I can control it.

6. Mind hair, glass and smoke

Fine hair, transparent objects and atmospheric effects are where keys fall apart. Backlight the hair to separate it from the screen. Avoid real smoke near the screen; add it digitally instead. And if a glass of water has to be on set, test the key on it before the take.

7. Shoot a clean plate

Before or after every setup, shoot a few seconds of the empty screen with the same lights and camera position. It costs ten seconds on set and can save hours in post, because many keyers use it to understand the screen's unevenness.

The habit behind the list

All seven points come down to one habit: think like the compositor while you are still the director. When the same person carries a project from the script to the final composite, that habit comes naturally, because the person who will suffer the consequences in post is standing right there on set.