What are the best practices for keying out green screen footage in VFX?

First up, we have our superstar: Green! Green is like that popular kid in school – always chosen first for sports teams. Why? Because it doesn't clash with most of our outfits (or skin, unless you're filming the Hulk). It’s a versatile color, easy to light, and generally stays out of trouble. Then there's Blue, the trusty sidekick. Blue is great when green is hogging the spotlight with things like, you know, trees or Kermit the Frog costumes. Blue steps in when green just can't cut it. But wait, there's more! Red, yellow, magenta... these are the rebels of the screen color world. Sure, they might give your VFX some trouble, and you'll probably spend months extra working. But hey, who doesn't love a good challenge?

Most people still use chroma green because it's not a color used in many places. You'll use blue with your subject needs to be wearing green, or there are green props, blue might be better. I've only used blue a few times, a couple of large outdoor setups with plants and when the person needs to be in green. We find it easier to key out with the green screen.

Planning is KEY. Along with the color, lighting and camera setup, talk to the VFX artists and ask for their two cents. Shots can be avoided from turning into a nightmare to key/comp if you ask simple questions at the beginning and not after the shoot. Tell the concept of the shot to the VFX person and see what they suggest might be the best approach. Just because you can shoot it with a certain setup, doesn't mean that it will yield the best looking shot after compositing.

Exactly! When I was the Composite Director at Turner Studios, I held a class on greenscreen compositing for our Directors and DPs to show them that spending a little more time on the shoot could save hours if not days in comp.

So, you're about to embark on the noble quest of green screen keying! First rule: Light it up like you're on a date with your screen - soft, even, and oh-so-flattering. We're talking mood lighting for your green screen, while your actors get the spotlight they deserve. Next, keep your actors far enough from the screen, like maintaining personal space on a crowded bus. You don’t want any green reflections playing tag on their clothes. Blocking unwanted light? Time for some blackout poetry with flags or black cloths. Keep those rogue rays at bay! And if you’re moving the camera, use tracking points like you're playing connect-the-dots. Just make them subtle; they’re not the stars of the show.

Always consult a vfx person before (and during) a shoot. Don’t trust these idiotic online tutorials that combine green screens with blue tracking markers. The less uniform your key color, the more characters will be eaten into by the key, especially things like hair. Always back-light the subjects and always have tracking markers (which are the same color but a different shade than the screen) in frame unless it’s a total lock-off.

Make sure your subject is brighter then the background. Use a high bitrate and codex as you can. A 4:4:4 color recording or RAW is ideal. The more pixels you have, the sharper a key you can get. Also get your subject far away from the screen to prevent the green light bounce from spilling over your subject. This is often the number one for a bad key. You'll need several lights to create an even lighting of the screen. Get that setup and perfectly flat on the wave forms on camera, then add your subject and light them separately. Watch out not to cast shadows of the subject onto the background. It doesn't matter your focus length in green screen, you likely want the person fully in focus, so often I'll stop down to F6-F8 dial it in.

I would add to this the importance of de-noising your plate footage with industry-standard software such as Neat Video’s reduce noise before pulling your key. This will remove unwanted flicker caused by digital noise or grain and give you the best results. Personally, I like to use the free, downloadable gizmo called DasGrain to re-introduce the original noise/grain structure back over the top of my final composite. Second thing to add, no matter how much distance you place between subject and screen, there seems to always be some level of spill - especially in blonde hair. Use HueCorrect (Nuke), DespillMagic (downloadable gizmo for Nuke), or whatever despill method you like to really get that subtle spill out. It’s worth the effort.

Avoid green clothing unless you aim for a floating head effect – it's a great party trick, not so much for serious filmmaking. Opt for colors that contrast nicely with your screen. Shiny hair or skin can reflect green. Use matte makeup and hairspray to avoid your actors turning into disco balls under the lights. Be mindful of reflective props. That shiny sword might look epic, but it could become a green screen nightmare. Keep your screen wrinkle-free and clean. Think of it as a high-maintenance houseplant – it needs regular care. Avoid harsh shadows. Soft, diffused lighting is your friend, creating a smooth, even backdrop for easier keying.