Achieving Optimum Chroma Key Lighting in Rainy Weather
Chroma key lighting is not subjective. It needs to be done a certain way in order for the effect to work. To understand chroma key lighting, you must first understand how the chroma key effect works before you can learn how to use it in challenging situations like rainy weather.
Step 1: Understanding How Chroma Key Works
The chroma key effect works by first isolating a specific color in the video and then keying it out. When a color is keyed out, it is turned into transparent video. You commonly see this effect done with green screens. An actor stands in front of the green screen and does his performance. The green screen is later replaced in post-production, and an illusion is created that the actor is in some far out crazy place. Because the color that is isolated is specific, the green screen must be lit evenly so that it's green color is consistent rather than being several different shades.
Step 2: Shooting in Rainy Weather in General
Shooting in rainy weather is a challenge without special effects. Equipment needs to be protected from the water because it could cause camera equipment to fry, creates risks for electrocution, and even presents opportunities for the glass on hot lights to shatter when they come into contact with the cold rain. You need to take safety precautions to prevent disasters from happening. But, that's another article in itself.
Step 3: Lighting a Green Screen in the Rain
So, if you're forced to use a green screen outside in the rain, there are a few things that you can do to make the best out of a bad situation. You should cover and keep the green screen dry. If the green screen gets wet, then it's going to be very hard to key it out. If it's a painted wall with water droplets, that's going to make the keying process very complicated because the green screen will no longer be one solid color.
You should cover the lights illuminating the green screen, and you should also cover the area between the light and the beam to prevent failing raindrops from being illuminated in front of the screen. Following these steps on set will save you and lot of time and headaches when you're applying the effect in the editing room.
Alternatives to Shooting in Rainy Weather
With all the special effects available to a filmmaker, there really isn't any reason to do a chroma key shot in rainy weather. Even if rain is required for the story, you can now easily add it in post production.
A chroma key effect is best attained when the green screen is lit evenly so it is one consistent color. Rainy weather ruins that, which makes the editing a lot harder than it needs to be. Shoot your green screen shot indoors and add the rain in later. If you really want the actors to get wet, then rig some kind of simple rain machine above their heads just for them.
If you keep your green screen shot simple, then you're going to have more room to enhance it with special effects. Shooting this effect shot in the rain is only going to limit you and will hurt your final product.