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EVERYTHING YOU NEED TO KNOW: SHOOTING WITH GREEN SCREENS
- Demis Lyall-Wilson
- 24 Jul 20
During Demis Lyall-Wilson’s career as a Hollywood VFX artist, he’s seen an awful lot of green screens. It’s practically impossible to be working in today's video/film/television industry and not wind up needing to chroma-key using a green (or blue, or even black) screen at some point.
What is green screen?
And what does it do? ‘Green screen’ is a VFX technique, where two images or video streams are layered, or composited, together. It’s usually a single coloured backdrop that an editor removes from the shot, to drop in other-worldly backgrounds or effects. Put simply, you’re superimposing one image or video stream over another, so it looks like one image.
The technique originally dates back to the 1900s, when blue screens were used, as it worked better with celluloid film. Why the switch to bright green? Well, it’s the colour furthest away from human skin tones.
Green screen setup: How do you do it?
It's not as easy as just pitching up big green rectangular sheet...there are couple elements involved that once you've nailed, will make shooting with green screens a smooth process...
1) Chroma key
What is chroma key?
This refers to the actual technique of layering, or compositing, two images based on colour hues. As every colour has a chroma range, this is where the phrase comes from. The chroma key singles out the selected colour – the green – and digitally removes it by rendering it transparent.
So, don’t forget, if you’re using green screen, then make sure your actor isn’t wearing anything green as part of their costume – a dress, or a tie, say – or you’ll end up with a transparent dress, or a tie-shaped strip down their front…
What is the best software for chroma key?
There's a number of software out there than can help you acheive the perfect chroma key, the best one will ultimately be the one that you can use with ease. Here's some of our top picks to get you started:
- ZS4 Video Editor: A new version of the Zwei Stein video editor, this software has more advanced editing and compositing tools available (over 150 built-in video effects) one of which is chroma key.
- Lightworks: Not only is Lightworks free, its been a staple in the video editing community for around 25 years, standing the test of time this software promises simplicity of use and high quality chroma key software.
- OpenShot: Another free and open source chroma key/ green screen software with rich video effects and cross platform functionality.
- iMovie: Free to download and perfect for mac users, who also want the option of shootin gon their phone!
- DaVinci Resolve: Free to use with functionality accross Mac/ Linux/ Windows.
This term is used to describe the process of removing the green screen in post-production using editing software.
How do I edit green screen?
Removing the green screen in the editing proccess is often referred to as 'pulling the key' - hence the phrase, 'keying'. Once you've figured out which software you want to use, usually you can remove the green in a couple of steps. Check out The Basic Filmmaker for his straightforward 3 min tutorial:
This refers to the coloured light that reflects back onto your subject from the green screen.
How to use green screen
Our guide will take you through all things green screen, plus Demis’s top tips on getting the best results with a green screen background and nailing the perfect chroma key, whether you’re shooting for YouTube, using it for news and weather reports, or video games, TV dramas and blockbuster movies.
Here are Demis Lyall-Wilson’s top tips:
1. Your goal is to create a single, flat colour
Some shades of green lean closer to yellow or blue, some lighter or darker. When you're setting up a screen behind your subject, try and get it to look as much like a single, unwrinkled flat sheet as possible, and it'll save you a load of time later. You might laugh, but a perfect example of this is Shia LaBeouf's infamous Just Do It video. Seriously. Just look at that lovely, flat screen. Compositors dream of perfection such as this…
2. Create as much space between screen and subject as possible
You might not have a lot of room, but try to make the most of whatever space you do have - ideally at least six feet between background and subject.
- Light separately: if you light the green background separately (bright and flat) from your actor, you’ll avoid them casting shadows (causing an uneven gradient) and any green hue bouncing off the subject, which causes problems when you’re removing the background
- More space will let you light your screen, while then setting up more ‘arty’ lighting on your actor
- Additional distance reduces how much ‘spill’ infects your subject (ie green light reflecting back from the screen, causing the actor’s skin to look pale and sickly)
- Depending on the lens, you’ll typically want around 25-30 foot depth for a full-length shot.
3. Green does not mean invisible
A compositor's biggest frustration is seeing a perfect screen set-up, then suddenly, a member of the crew runs in front of the actor dressed in (head-to-toe) green spandex, essentially ruining the shot. There are very few occasions where this is necessary, and it often causes more problems than it solves.
4. Ensure your screen covers the entire area you're shooting
This might sound like common sense, but you'd be surprised how often it doesn't happen. How do you suppose the compositing artist might have chroma-keyed the top of the actor's head, or those leaves in the background? Answer: with great difficulty (or a lot of rotoscoping, and additional CGI)
5. Watch and learn !
Like most of the technical black arts, the trick to good green screens is practice and experimentation. Even if you don't plan on becoming a compositor, it will also help to watch a couple of keying tutorials to understand the issues they face. Knowing exactly how the screens end up being used in post-production will teach you everything you need to know to set up and shoot the perfect green screen on set!
How to make a green screen
You may have a vision of multi-million dollar blockbusters with huge amounts of tech, but it’s easy to create your own green screen. All you need is a smartphone or webcam, some fabric, lights and video editing software.
Here’s the step by step for a green screen setup:
1. Get a backdrop
Get a cloth or collapsible green screen panel in bright green – look for colours such as ‘chroma key green’ or ‘digi green’. You need a non-reflective material and if you’re using fabric, then make sure you’ve ironed or steamed it to get rid of any wrinkles.
You can also buy a green screen kit – from small portable screens to full-size for a more permanent installation. These can be useful if you’re filming on the go.
2. Use a ‘coved’ green screen
For the best results, and to show your actor from head to toe, the screen needs to continue down the wall, and onto the floor under their feet. A cove – a curved corner where the wall meets the floor – will smooth the transition from wall to floor, avoiding shadows and hard lines that can cause gradient changes.
For wider shots, or action shots that require lots of movement, you’ll need to scale up the size of your green screen.
3. Set up your lighting
Remember, you need to light your foreground and backdrop separately – and think about lighting your character in order to match the lighting of the environment they’re going to be in once the green screen is composited.
The key to even lighting is to use large, soft light sources (hard light sources with no diffusion will create hot spots on the background.) On a budget? Try mounting a white sheet on a C-stand a few feet in front of your light.
Here’s a useful ‘how to’ on lighting green screen if you’re on a budget:
4. Don’t forget – allow depth
Back up the camera to allow you to fit in your actor from head to foot – plus at least 6 feet between your actor and the green screen to minimise ‘spill’ and unwanted shadows.
5. Keep your camera still
Lock down the camera to avoid the subject looking as though it’s vibrating against the background if the camera moves. And eliminate any motion blur by filming with a faster shutter speed.
6. Green screen video editing software
For the green screen video editor, there are plenty of great free software options available, such as DaVinci Resolve and HitFilm Express. Or for expert advice, check out our guide to the best Premiere Pro tutorials.
Need help with sound recording to make your shoot go smoothly? We have the ultimate sound recording tips for you.
And then, of course, to complete your green screen extravaganza, you’ll need music. The Audio Network catalogue has over 175,000 tracks to licence – and there are hundreds of hand-picked playlists to make finding that perfect track simple and fast. Covering everything from YouTube to film scores and trailers and for SFX and other soundscapes, check out the Editor’s Toolkit.
So, now you’ve got all you need to know to go out and create fantastical worlds with green screen, where the only limits are your imagination!
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This page was originally published in 23/11/2016 and updated on 22/07/2020
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