Is the masking feature in 2.1 and 2.5 only for allowing separate chroma key control for up to four zones because of chroma key color variation in an image or can it effectively be used to "cut out" unwanted parts of the image that are not chroma keyed but need to be (called a garbage matte I think). I can see wanting to insert the chroma keyed portion of an image into a scene but my green screen was too small to cover the whole frame. In other words, I would like to mask out garbage and use the green screen for only the fine separation of actor and background.