Green screens are among the most powerful tools in the hands of expert film and video makers since they allow them to separate the subject from the background during the post-production process. After separating the green background, they can replace it with another background of their choice to achieve a result that may have been, otherwise, impossible to achieve or hazardous and expensive. Many of the special effects in the films we see nowadays would not have been possible without the expert use of green screens.
Green Screen Technicalities
After you have shot the subject against a green screen, you will need to key out the green color of the screen by undertaking a process called chroma keying. You are left with only the subject and transparent background to which, you can add a new background, according to Infocus Film School. An extremely technical process that calls for a high degree of expertise, chroma-keying adds significantly to the content’s production value. Some tips for working with green screens:
Ensure Even Lighting
It is vital to keep the screen lighting even because uneven lighting can cast shadows, making it difficult for the chroma keying software to distinguish between the dark and the light greens. Arranging the lights to achieve soft lighting on the green screen is integral to good video production.
Eliminate Green Clothes and Accessories on the Subject
If your subjects wear anything green, the chroma keying process will remove the green color since it blends with the green screen background. It means if your subjects wear green clothes, the clothes will disappear. However, this factor comes in handy if you want to eliminate a body part from the final shot. Covering a limb with clothing colored green can make it seem it was amputated as the green is keyed-out during post-production.
Put Distance between the Background and the Subject
Shadows, the bane of chroma keying, can make life very difficult for editors. To avoid shadows in the background, you must put sufficient distance between the subject and the green screen. If the subject is right against the screen, it will not be possible for you to ensure even lighting of the screen behind, however, if you put some distance between the two, you will get enough space to place lights in such a way that the screen is lit evenly.
Use Low Aperture
When you use a low aperture setting on your camera, it results in a lower F-stop number that, in turn, makes the depth of field shallower. When you put some distance between the subject and the green screen, keeping the subject in sharp focus automatically makes the green screen appear softer, which helps to make it more uniformly colored.
Using a green screen opens up a world of opportunities for filmmakers. However, even though the technique is conceptually simple, executing it to achieve a realistic result is a complex matter calling for a high degree of expertise and experience. It is also a relatively costly process, but then it allows you to shoot in the safety of a sound studio without exposing the actors and the crew to on-location hazards.