I've been using Spectramatte successfully for a long time but encountered a problem recently. My subject is wearing a black business suit and I'm getting tearing/bleeding in the blacks. It looks fine in MC and on the client monitor but the problem occurs after I export from MC and transcode to mp4 in Squeeze. I can fix the problem by increasing matte blur and adjusting the alpha offset. The rest of the shot--skin tones, hair--keys beautifully.
The footage was shot in Slog/3CineEI on a FS7 and I applied a Sony LUT (SGamut3CineSlog3_To_LC-709TypeA) to the source footage. Before keying, I raised the blacks in CC to bring in some of the detail in the jacket, but that should not affect the color.
I'm curious why there would be a problem in the blacks, since theoretically there is no green in the subject's black jacket and he is facing there camera, where there is absolutely no possibility of green spill?