Definition
What is chroma key?
Chroma key, often called green-screen or blue-screen keying, removes pixels within a chosen color range from footage to create transparency. The isolated subject can then be composited over another image or video layer.
Green and blue are common screen colors because they are distinct from most skin tones and can be captured efficiently, but chroma keying can target any suitably consistent color. A clean key depends greatly on production: an evenly lit background, separation between subject and screen, and limited spill make post-production faster and more convincing.
Keying software creates a matte that distinguishes opaque subject pixels from transparent background pixels. Editors refine that matte by adjusting tolerance, edge softness, and spill suppression, then match the foreground’s color, perspective, light, and shadow to the replacement background.
Example in the edit
A weather presenter is recorded against an evenly lit green backdrop. In post-production, the green is keyed out and a moving weather map is placed behind the presenter.
Why editors use it
Chroma key makes locations, virtual sets, demonstrations, and visual effects possible without physically building every environment. Careful setup saves significant cleanup work and produces more believable composites.
Watch and learn
See the technique in context
Selected explanation by Adobe Video
Quick answers
Frequently asked questions about Chroma key
Why are green and blue used for chroma key?
They are usually easy to distinguish from skin tones and from many costumes. The best choice is the color least likely to appear on the subject and easiest to light cleanly.
What causes a poor green-screen key?
Uneven screen lighting, wrinkles, shadows, motion blur, compression, and green light reflecting onto the subject can all create rough edges or unwanted transparency.
Is chroma key the same as compositing?
No. Keying creates transparency from a selected color. Compositing is the broader process of combining the keyed footage with other layers convincingly.