why lighting is important when using a green screen, explain below why it is important

Bad green screen and lights result in an uneven tone on camera. Some areas look darker than others. The darker areas become harder to chroma key out afterward, especially if there are transparent objects or fine hair within the shot.

The most important aspect of shooting any type of green or blue screen project is the appropriate lighting. If the subject isn't lit correctly or the green screen is too dark, too bright, or uneven, chances are you'll have problems pulling a good matte