black and white, gradually overexposure

[dark cloud SA]

i am shooting a black and white short and need advice about achieving certain effects. (shot on DV in colour so as to retain contrast then converted to B&W)
Firstly i want to gradually overexpose the image and pump up the contrast as the narrative progresses.
Apart from this i want to have a single element in the film that is in colour, namely a red door.

1)is it possible to achieve this overexposure in realtime or would it be necc to cut between shots where the exposure changes (i will be editing on Final Cut Pro HD)

2) What will be the most effective way of achieving this effect. Should the door be painted red and then all colours but red be removed from the image (i'm worried about this effecting skin tones and sneaking elements of red on the set only becoming apparent when it is too late.)

Or can it be rotoscoped in After Effects (i have access to a FX guy who is proficient in this program). i need the red to look semi realistic however, and wonder if the overexposure of the image will be of consequence in this regard.)

Does anyone have experience in this? Any advice will be appreciated.

 

[MarkG]

I can't comment on FCP specifically, but you can change the exposure on a shot by playing with the color correction tools in any decent editing program, so that shouldn't be too hard. Most should also give you the ability to eliminate all but a narrow range of colors from a scene, so I'd try painting the door red and see if you can narrow it down enough that it doesn't also affect skin tones. In the worst case you'll have to rotoscope the whole thing, but you'd have had to do that anyway, so no real loss.

Certainly I did a scene on a friend's movie a while back where everything was black and white other than the blood on a dead body, and Premiere's filters were enough to separate out the colors that way.