If you plan to shoot a lot of chroma key, you may invest in a dedicated chroma keying system. We use a Reflecmedia Chroma Key system frequently. This approach relies on a LED disc attached to the camera lens that reflects light on a special fabric containing millions of glass beads that reflect the lower powered light and create an even-colored surface. Systems like this cost more, but are popular for their ease of use and portability. The system saves us a lot of time and money during the editing stages.