Green Screen Basics

Leonardo DiCaprio in The Great GatsbyWith the recent release of Baz Luhrmans ‘The Great Gatsby’ and their behind the scenes video on the use of Green screen work in the film I thought it would be a great opportunity to do a post about shooting your own green screen.

Green Screen is a fantastic tool for filmmaking that open up so many storytelling opportunities. It isn’t too difficult provided you know the basics and is easy to use for your films whether you are making an independent low budget film or Hollywood Blockbuster.

I thought I would start with the bare basics for those who haven’t tried it before or if you are looking to brush up old skills.

Life of Pi Green screen effectWhat is a Green Screen?

A green screen is usually a large piece of special fabric or a studio space that has been painted the same colour. This is a tool that allows you to replace anything green that you have filmed for something else in post production.

What Do You Use a Green Screen For?

Green screens are a key tool in a technique called chroma keying. In a basic scenario this may involve a person/subject being filmed standing in front of a green (or blue) screen. Then using an editing program the green colour is digitally removed from the video file leaving the person/subject. A new image/video is then superimposed behind them. If done well it should look as though the person is actually standing in the scenario that is happening in the background.

The ability to chroma key opens up an array of options for filmmakers. For example if you are filming a news story and you need your presenter to look as though they are standing out the front of the Taj Mahal, then you could use this technique instead of ACTUALLY taking a news reporter to the Taj Mahal. It saves a lot of time and money.

Why Green?

There are both blue and green screens. It really depends on what your subject is as to which might be better for you. Green is generally more popular as most video camera sensor are more sensitive to green. Because of this it means that it will produce less noise and will help you create the cleanest key/matte/mask.
Green is also common as you may have a subject with blue eyes or jeans. If you were to use a blue screen for that then their pants would also disappear. Oh dear! 

What you need to get started

Basic Green Screen Setup* A green/ blue screen cloth and stands or wall.
Ideally use a professional standard one though these can be expensive so if you are on a tight budget check out Jeff Geerlongs DIY guide to making your own green screen and frame.

* Lights and stands
Watch the video below for tips on choosing your lights.

* A camera
Choose carefully as some cameras are better suited to green screen, especially if you are shooting something with a bit of movement. (In my next blog post I will be going into depth about choosing the best camera for green screen.)

* A post production workflow
It’s best if you know how to handle compositing in your editing software before you start so you have a better idea of what you need to get a good result. Try practicing with some test footage.

The Basics for Lighting a Green Screen

Ehran Edwards on set 'Five Poison Arrows'

Ehran Edwards on set ‘Five Poison Arrows’

Some great tips to keep in mind when setting up your green screen shoot.

* Ensure your screen is as taught as possible.

* Evenly light your screen so that the colour is consistent.

* Match your lighting to the lighting environment that the subject will be keyed into. Very important

* Ensure the props and costumes are suitable. If either of these things have green in them, BEWARE because the colour may be extracted in post if the colour is similar.

* Tracking markers. If you are planning on having camera movement or you are putting a computer generated background then you will need markers. This may seem quite complicated, but provided you get it right from the start you can save yourself a lot of time in post (trust me, I know). If you haven’t done green screen before then this motion tracking video by Micromedia SA might seem very challenging but it will give you an idea of what tracking markers are used for and the potential of green screen.

Here is a fun and in depth video from WireCast Tube which demonstrates these and also has a few tips of their own. ‘How To Light A Green Screen Effectively

Here is another great video from Adorama TV which is a bit more in depth and also covers shooting green screen with a DSLR.

 

What do You Do Once You Have Finished Filming?

Getting Rid of the Green

Once you have imported all your footage and brought it into your editing software it is now time to get rid of all the green.
Every editing program handles chroma keying differently. There are a lot of tutorials online to show you how to do this.

Here is one example of how to use the green screen functions in Final Cut Pro by Justin Thyme.

What if you didn’t light your green screen well?

All the magic of a green screen happens in editing. But what happens if you haven’t lit your green screen properly? Occasionally you may find your lighting was uneven, perhaps there was a shadow or an unwanted item in your shot. This makes it hard for your program to remove all the green which may mean splotchy blobs of green all through your video or your actor looking like a cardboard cutout. Either way the audience won’t be impressed.

So here are a couple of links to videos I found useful when I was in my time of need.

Machael Stark has a fantastic video for fixing up your bad green screen work using Colourista 2. Click here for the video.

Surfaced Studio shares 5 common green screen mistakes.

Examples

Stephanie Cherote ‘Five Poison Arrows’

This is a music video I filmed, directed and edited. I learnt a lot about green screen through my mistakes on this production. The green screen is featured in postcards. In the video this meant filming the subjects then putting in the background, then placing that inside a computer generated polaroid frame then putting that into the main video to follow the motion of the moving camera. Considering I had no idea what I was doing at the time, I am pretty happy with how this turned out. But i can’t encourage you enough to do as much research BEFORE you shoot as you can save a lot in post but it’s time you could have saved.

Dane Rumble ‘Lights Go Down’ Music Video

Here is a music video I worked on last year which used green screen and motion tracking. Check out the behind the scenes here.

The Great Gatsby VFX

I hope that you have found this post helpful. Good luck with your shoot and be sure to watch out for my next post on green screen where I go into a bit more depth.

Ehran EdwardsIf you liked this post please ‘LIKE’ my Facebook page and ‘FOLLOW’ my blog. I keep them up to date with; projects I’m involved in, reviews & tutorials and share interesting tid-bits to make you smile.

“With my head in the stars, a twinkle in my eye and a love for cinema and nostalgia, filmmaking is a fun, creative way to express myself.”

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