Compositing is a technique for combining images from various sources into a single video. A section of one video is cut out and layered on top of another. The chroma key is the most common method of editing out a portion of an image, in which all objects of a single color are removed from the image. The most common colors are bright green or blue. Because an actor or presenter is usually recorded in front of a blue or green backdrop, video compositing is also known as bluescreening or greenscreeening.
A suitable backdrop is required when recording for video compositing. For the video compositing process to work properly, the backdrop, whether blue or green, must be smooth and properly lit, and the screen must be large enough to accommodate the entire shot. Clothing and foreground objects that are the same color as the backdrop are not permitted.
When recording a video for compositing, the backdrop is crucial. To edit away cleanly, it must appear as an even field of either blue or green. Any bright spots or dark shadows in the image may be distinct enough to stay. A smooth, evenly colored backdrop with a matte finish and no discernible pattern is required. Painted walls are the most straightforward, but cloth backdrops designed specifically for video compositing are also available.
When selecting a backdrop, size is also a factor to consider. The backdrop must be large enough to completely fill the image. A small backdrop will suffice for a stationary presentation. However, if the subject must move, a much larger background is required. It may be necessary to chroma key the floor and other objects in some cases, such as when the subject is to appear to fly.
To give the backdrop the even appearance required, proper lighting is also required. To avoid the subject’s shadow appearing on the backdrop, the subject and the backdrop must be lit separately. Three diffuse lights, one overhead and one on each side, are recommended for the backdrop for best results.
For chroma key video compositing, either blue or green can be used, but it’s important that the color chosen doesn’t show up in the rest of the image. Green clothing and objects, for example, should not be recorded in front of a green screen unless they are being deliberately removed from the shot. Accessories and ties are frequently overlooked, resulting in unintentionally amusing results.