Chroma Key

In CHROMA KEY the subject is shot in front of a blue or green background. The subject is then keyed over a background of live or pre recorded video.

These days it can be done using an editing program like Premiere, Premiere Elements or Pinnacle Studio. Where the background is green in the case of a green key or blue in the case of blue key, the background colour will become transparent and the pre recorded video will show through. This is most commonly seen when Superman flies over tall buildings. He is actually recorded in a studio in front of a green background. then keyed over video of the buildings.