The Fast Color Corrector and 3-Way have Levels controls built into them.
Try this: Set the input black and input white (RGB) values to the same number in all three plug ins.
Now, compare the looks between each plug in separately.
What I'm seeing is that they're all different.
I think they should be identical.
Bug? Feature? "Interesting" programming choices?
Top to bottom order: Levels, 3-way, Fast
Mac 10.7.4 - CS601 - Quadro 4000
Here's what I noticed.
Levels will constrict the change to Broadcast legal levels, 0 to 100 IRE.
Three Way will crush into 0 IRE, but allow illegal, over 100 IRE levels.
Fast Color Corrector will allow both below 0 and above 100 IRE levels.