To begin the discussion, colorist Mike Most (NYPD Blue, LA Law) explains the need for colorists:
It’s the nature of ﬁlm and or videotape that you can’t just develop it and put it on a telecine in some automated way and make it look okay. I mean, somebody’s gotta be at the controls, controlling balance and brightness and color and there’s a whole bunch of reasons. But the basic fact of the matter is that it’s not locked in. That’s the beautiful thing about shooting ﬁlm is that you have a lot of range and you can change it in post. That’s one of the reasons why a lot of cameramen are loathe to go to HD video, because that range is severely cut down. And the nice thing about shooting ﬁlm is that you can play it straight ahead and straight down the middle, or you can turn it into something special and that’s where a colorist comes in. It’s not just about balancing both sides of a scene. When things are shot single camera, they’re not shot at the same time under exactly the same lights, you shoot one angle, you relight, you turn around you shoot the other angle, and those two things have to match. Even if you have the greatest cameraman in the world shooting tape, they’re not gonna match perfectly. Somebody has to sit there and balance them. So that’s where the colorist comes in.