Everything you need to know about Blue/Green Screens

Throughout my various videos, I have been asked many questions regarding green screens. Below are some of the more common questions I’ve been asked. Hopefully after reading this you can go out and make your own special effects videos or incorporate green screens in a video you make.

 

Why green/blue?

The reason both green and blue are used is because we have no green or blue in our skin. Basically you should choose the color that is the LEAST prominent on your subject. Unless he/she is specifically wearing blue or green, then the difference is minimal. When the color is removed from the footage, you are left with just your subject without any background. By having a person or object by itself, you open up countless options to play with.

 
What would I use it for?

The goal in using a green screen is to isolate the subject. With just an isolated actor, the effects creator can literally do anything. They could put that person anywhere on the world. That person could artificially be made to fly. That person could still be moving while everything else has stopped. Or that person could teleport away. In After Effects (the program that I and many others use to make special effects) everything is viewed as layers. By having just that person (or whatever other object you decide to use) isolated, he/she can be toyed with and made to do anything independently of his/her surroundings. This is a very useful skill to have.

 

What shade of green/blue should I use?

It all depends on what you are shooting/wearing. But usually the best blues or greens are the brightest. Darker colors tend to take away more from the footage but if you have a bright green or blue screen it should key out just fine. For the best results, use this shade of green and this shade of blue.

 

What is the difference between a blue screen and green screen?

As I said above, the reason that blue or green are used is because we do not have much blue/green in our skin color. Now, personally I believe the decision between the two colors is up to the director or effects engineer because the difference is minimal. I have heard that blue is better for brown/black-haired darker skin people and green is better for blonde light-skinned but either way it is, as I said, up to the preference of the user. If you are going to have either blue or green in the scene, I would suggest using the contrasting screen (Has a nice ring to it doesn't it?)

 

What should I use?

Any blue or green material can be used. Preferably the material should not be too thin, because then too much light will pass through it and you might pick up whatever is behind it. I would suggest going to a fabric store and picking out a semi-thick sheet of the desired color. But for just starting out any fabric would do. Make sure that it is a solid color with no designs or special texture on it. You want something that resembles this. Eventually you might want to upgrade to an official green/blue screen. Another option is to go out and buy green/blue paint and paint on an object. This would allow you to simulate different things. A chair painted green for example could be sat on and keyed out to make it look like the person is levitating. I saw an example of someone who painted a cardboard box shaped as a tv green to simulate the Ring effect. Whatever you choose, make sure to get a bright/solid of a color as possible.

 

How do I use it?

You can either use a green screen stand, some kind of frame that will hold the sheet up, or you can even have two people hold it. The main purpose of the screen is to completely cover the subject. Make sure when you film, that the subject on the green screen is completely outlined by green. This holds true if they move as well. Either have the screen be picked up to follow him/her or have a bigger sheet. The purpose for this is so that when you take out the color from behind them, you just are left with the subject. If there are other things that surround the screen, simply mask them out with a rectangular mask. Also, make sure if you are holding a sheet to not have any ripples. This creates shadows and a noticeable texture on top of the layer.

 

What should I use to get the green out of the footage?

I personally use Keylight 1.2. You can download this here. Plenty of other programs work as well and for the simplest techniques, just go to Effects->Keying and choose one that suits you. Keylight works amazingly well. It allows you to toy with the settings until you reach the desired effect. These programs are not miracle workers, however, so make sure your footage is up to par as far as lighting the blue/green screen.

 

What do I do if the person is not completely covered by the green screen?

If you are unable to have blue/green behind the person for the complete duration of the footage, you will have to frame-by-frame outline the parts of your subject that leave the green/blue. This is tedious work and I would highly suggest re-shooting instead of having to do this. If a reshoot is not possible then use the mask tool in very much the same way as I show in the lightsaber tutorial. Simply outline the desired parts of his/her body and follow them as they move.

 

Anything else I should keep in mind?

 
If used right, blue/green screens can add a very professional feel to your film without having to spend loads of money on a set or special effects. I would suggest checking out many of the great after effects tutorials around the internet to get familiar with what it is capable of, and then messing around with some sample projects. Try to make your mom or dad fly around New York City. Turn into Godzilla and stomp on poor civilians. Or, stop time and walk around in a frozen world. Whatever you decide, show me what you’ve done, and I will give my feedback.

 

 

 

 

 

 

 

 

Did I miss something? Email me at RT@ryanturnerproductions.com and let me know what I can add!