Green screen is a technique where the green element in the picture is keyed out, this means the green is erased in post production and replaced with other video or images of some sort. This is an old Hollywood trick that is used to create computer generated images and composite scenes that are impossible to achieve in a camera or that are just too expensive to create in camera.
We at Octopus Films Sydney are experts in shooting green screen and if all this looks too hard feel free to call us to come and do it for you. We can bring everything needed to your office, factory or warehouse to get the job done right. So heres how to do it.
There are four main points to consider and control when shooting a green screen set up if you want a great key (key being the term for the removal of the green area).
1. Use a camera that has a higher than average bit rate and decent colour space. We, at a minimum, use a Canon C100 recording to a Atomos Ninja 2 set to Pro Res 422. The better the cameras specs the better the key will be.
2. Even lighting across the green screen. Not imperative but it should be at least fairly even. This will make your video editor or compositor much happier as their job will be made easier.
3. Control green spill, stray reflected light, from the green screen background on the subject.
4. Make sure the colours of or on your subject are not the same as they colour of your green or blue screen.
The main thing you need to do is make sure your lighting is correct and that your subject is not wearing green (assuming that your subject is a person). If having green on your subject is unavoidable you can use blue or any other colour you like, typically the chroma key area (green screen) is green or blue.
A typical green screen lighting set up that we use consists of 4 lights and a reflector. This is just enough to shoot a one or two person in shot green screen set up using a 2.8m wide green screen. The lights we use are two daylight kinoflo divas for the green screen background. One Kinoflo daylight Diva for the subject with a silver reflector on the opposite side of the subject and one dedolight 150w gelled to daylight as a backlight.
The lighting across the green screen section of your image should be nice and even as this will make the green screen area easier to key. The subject is lit with the key light, any way you want really and the back light is important to help control green coloured light spill bouncing off the green screen.
There is not too much more to it other than that. Other tips would be to keep fly away hair under control as keying in between hair can cause issues and try and keep your subject to background distance at least two meters if possible which will make it easier to keep the green light from spilling on your subject.