Ever wonder how film productions easily snip people or objects out of a frame and place them in a completely different environment? The answer lies within one colour - green! And Blue actually in some cases used mostly in movies for CGI.
Using something so simple as a green screen during film production can transform your footage from the ordinary into the extraordinary, or even bizarre. In this post, we’ll go over what a green screen is, ways you can set one up and some handy tips to get the most out of your editing.
What is a green screen?
A green screen is used to cut (chroma key) a person or object out of your footage so that your background it can be replaced without affecting the person or object you want to keep in shot. For example, a person dancing in front of a green screen allows for them to be placed in a different location. You can do the same thing with a window with a green screen behind it so that you can change what the outside looks like. Wonder how the newscasters show you the weather forecast and storm fronts? They’re all standing in front of a green screen.
The reason green is used primarily is due to the difference in pigment compared to human skin. Because the colour green is not overly prevalent on human skin, it makes it the perfect colour for what’s called keying. Keying is the act of removing the person or object from the image during the editing phase.
Nowadays keying is done by taking the footage into your program of choice (ie Adobe After effects or Premiere) and then using a colour key. With the colour key you choose what colour the program should look for and the tolerance for how picky it is, then the program removes that colour leaving a transparent area in its place, this can be very clean or it may have a lot of static depending on your footage. See the handy tips below on how to prevent static from happening.
But green isn’t the only colour used. Blue tends to get used a lot for action sequences in major motion pictures. There are even cases like the predator suit from the original Sci Fi thriller Predator being a bright red so as to contrast the jungle it was supposed to be invisible in during editing.
Choosing the right kind of green screen
If you’re ready to take the plunge and start using a green screen in your video production, it’s worth considering a few things before buying the most expensive or largest green screen. Here’s a few things to ask yourself:
How often are you going to use it?
How easy is the screen to put away and store?
How large does it need to be?
Will the green screen be used indoors or outdoors?
If you’re on a budget, don’t have a lot of space or simply won’t be using a screen very often, it’s worth considering doing a bit of DIY. Using a matte finish green paint, or finding green paper or muslin cloth and sticking it to the wall will work just as well in most cases as a pop up green screen. Always use matte finishes, as shiny or glossy materials will reflect light back into the camera, possibly ruining your shot. The most ideal shade of green is RGB 0, 177, 64, CMYK 81, 0, 92, 0 or Hex #00b140.
Handy tips when using a green screen
Once you’re green screen is up and you’re ready to get creative, there’s a few handy tips to keep in mind to get the most out of your video shoot.
Always remember to light properly. You don’t want any shadows on your subject or the screen, so always use professional lighting indoors, and you just might be able to get away with natural light if shooting outdoors.
Anything that you’re cutting out of the final image needs to be green. So if your object is sitting on something in front of the green screen, then the seat needs to be green too so you can easily cut it out during editing.
Always separate your subject from the green screen backdrop so you don't get what's called green screen or chroma spill. This is where the green tinge will reflect onto the persons shoulders and hair, making it extremely hard to key out the background separately cleanly. To prevent this, always have at least a 1.5 meter distance from the backdrop and the subject, then light your subject from behind to further eliminate any spill.
Have an idea of what your background will be. This will help you determine your focal length between subject and camera, and what the focal length can look like between subject and new background that'll replace the green screen to have the most realistic look.
If it’s the object you’re wanting to modify in editing, then that must be green. Think of all the CGI animals from the latest motion pictures. When they’re being handled by an actor, they’re actually handling a green covered object.
So there you have it, a basic run down on what a green screen is, plus some tips on how to get your hands on one and how to get the most out of your green screen. Like this article and are keen to learn more on what you can do with your camera and a green screen? Why not take one of our short film production courses! Check out our courses page to learn more.
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