Whether for shooting corporate videos or short films, nearly every videographer or penny-rate filmmaker has had a situation where they want/need to use a greenscreen for a project. Rest assured, most uses of green screen are done incredibly poorly, and it comes down to two different problems: people don’t take the time to key their footage, thoroughly, and they do a poor job of lighting the green screen. Learning how to key correctly is a science in and of itself, but green screen lighting can be done right, with time and patience, and will save you a lot of time in post-production. Here are some tips that can help you learn to properly light a green screen…
Get a large enough space
First of all, you can’t light a green screen, correctly, in a small space. Trying to light a green screen in your bedroom is going to end with a massive amount of spill (green light bouncing around the room). Lighting a green screen takes space to do right. For this reason, it’s important to get a large space to utilize for your green screen shoot. Ideally, this means a studio or a sound stage. However, if need be, you could make do by converting a warehouse or a garage into such a space.
Know when to use blue or green
While we usually refer to the process as “green screening,” you’ve probably noticed lots of behind-the-scenes videos use a blue screen, as well. The reality is that you can use both, and typically want to do so for different reasons. Green screens are more popular because subjects are less likely to be wearing green, and you tend to get less noise in your image when you are keying out green. However, green screens also tend to be brighter than blue screens, and this can make it difficult to clean up the outline around a subject’s hair, while keying. As a rule of thumb, you want to use green screens when your subjects have darker hair, and blue screens whenever your subjects have brighter hair (or if you are doing a low-light scene).
Using a green screen requires a lot of specific lighting equipment. First of all you want to make sure that you have the right types of lights for green screening, which usually means using softer lights that won’t be as directional. Strong directional lights will cause a lot of spill to bounce back onto your subject. In addition, you want to use a mixture of flags and diffusion to evenly light the green screen and keep that light from bouncing around.
Be conscious of your angle of reflection
When you light a green screen, you don’t want to point your lights directly at the backdrop. This is for two reasons: one, it will be difficult to spread light evenly across the whole screen, and two, this will cause the light to bounce directly back onto your subject. For this reason, you want to put your lights off to the side of the green screen and have the stream of light spread across as much surface area as possible. Most digital cameras have zebra line tools that can help you determine a green screen is evenly lit.
Light your subject separately
Once your green screen is an even shade of green, you want to light your subject separately. None of the light that is affecting your backdrop should be hitting your actor. The important thing to do here is make sure that you light your subject so that they stand out from the background. Consider what type of background you will be keying in behind them, and light them to reflect that background. The way you light your subject is one of the most important parts of a successful keyed shot.
If you’ve ever tried keying a shot before, then you’ve probably noticed hair is one of the most difficult things to key. Typically, a poorly keyed shot will have a ring of green around an actor’s hair, or else half of their hair is missing, since it is being masked out by the keying tool. One little tip you can use to make this process easier in post-production is dropping a backlight in on the subject’s hair. A strong hairlight coming from behind the subject will help separate them from the backdrop, and gives their hair a more distinct shape for you to key around.