When we discuss chroma key lighting techniques, there are many things that need to be considered in order to achieve the best results, quality, and setup for the actual image overlays to be completed in the production and editing departments.
Not only green screens anymore While we talk about green screens throughout the industry, almost as an exclusive topic, we neglect the traditional blue screens of the past.
The techniques for lighting are predominantly the same for both screens, and since green screens have become the primary backdrop for compositing technology that is the format we will discuss the most.
While green screens are used in nearly every capacity of video recording and production today, there are a few instances where blue screens will be more suitable and ideal.
It all begins, and ends, with lighting If your backdrop lighting technique is sub par, then your entire production and final product will suffer.
Lighting a chroma key setup isn't simply about capturing the perfect essence of the actor, but about avoiding shadows, undesirable color combinations, and reflections that may not be visible during recording, but will rear its ugly head upon composite overlays.
There are those in the industry who advocate for perfection of lighting when using chroma key techniques.
Their design and layout of different lights is carefully constructed, tested, measured, and retested before any shoot is to begin.
This may be ideal for big budget films, but it isn't always necessary.
The main idea for proper green screen lighting technique is to maintain an even distribution of lighting.
Outdoor sunlight under a white cover, such as a tent, is one suitable light source that can be used.
However, there are many issues that can arise during a shoot when relying on this technique, such as clouds passing overhead or shadows that may be imperceptible at the time of shooting.
Using a chroma key background in a controlled environment is ideal.
The ideal set up for green screen lighting is either a four or five light approach.
Start off with a basic 3-point lighting plan on your subject.
This will include a Key, Fill and Back light.
- Key light - This is the main light source that angles down toward the actor.
Care must be taken to ensure this light does not spill onto the green lit background. - Fill light - This light will generally be positioned at an angle to the side of the actor opposite to the key light.
Ideally, you will want this light to be less intense than the key light resulting in some slight shadowing.
This will help create the illusion of 3 dimensions. - Hair light or Back light - Some shoots demand a bit more light from above so that the actor's hair, or head, isn't lost in the composite overlay upon editing.
This light source will help separate the subject from the background. - Green screen light - This light will illuminate the green screen itself.
This fixture should be flooded out to ensure a soft even cast of illumination.
The fixture will be aimed at the background from a 45 degree angle. - 2nd Green screen light - Set up the same as the first from the opposite side of the set.
Proper chroma key lighting doesn't stop with the lights themselves.
When filming, you want to make sure that the actor, or any images that you're using for the shot, are at least six to eight feet in front of the screen, when possible.
Failure to adhere to this could cause shadows that will be picked up once the background overlay is inserted in post-production.
Also, make sure that there are no strings, such as those hanging from clothing, or loose hair strands.
These can cause issues once the background is inserted.
Proper green screen lighting is essential to ensure a successful chroma-key result in post-production.
Take the time to lay everything out before you shoot so that once you get into the editing room, your background will look seamless against the actors.