What is Green Screening?
Through the magic of green screening effects and technology, you can now superimpose your subjects onto virtual backgrounds anywhere, essentially pulling them out of the real world and placing them onto a digital domain by means of the chroma-keying or color-keying process.
Keying is the process of isolating a single color or brightness value and using software to make that value transparent, allowing another image to show through the affected areas. In fact, you can key out any color; red, yellow, purple or pink, blue and of course, green.
So why is that odd and ugly shade of green the hue of choice for video? The biggest factor is simply contrast. In order to isolate one area from the rest, the background color must be distinctly different. Any clothing that matches the background too closely will also key out, punching a hole in your subject’s body, or making them invisible altogether. Thankfully green isn't a common colour with people and most objects.
Green screening can happen in specially designed green screen studios, or using portable green screen backgrounds erected on location. Uniform lighting of the green screen background is critical to facilitate successful keying in the post production or editing process. Special strip-lighting kits are available for portal green screen setups.
When to use Green Screening
Green screening is a special effects strategy and, like all special effects, should be used sparingly. If executed poorly, this technique can reduce the integrity and credibility of the shot.
At On Point Video we use green screening when we cannot find a relevant, suitable background for an interview subject on location. Or when we need to film multiple interviews in a short period of time, and we need to vary the background to give the viewer some visual relief.
Additional Information Links
- Chroma Keying on Wikipedia
- Green Screen Equipment at Vistek.ca
- How to light a Green Screen from B&H
- Filming with Green Screening from InFocusfilmschool.com