motion chroma key-ing

[Kevin Camp]

i would try to shoot around compisiting problems next time, and go with static shots and cuts.

if you really need a moving camera shot, you should place some tracking dots on the green screen, but even this won’t make it easy. you’ll usually have dots that move behind somehing and you’ll lose the tracking, then you’ll have to track another dot to continue the movement, but offset the value so as to match the position of the previous dot. it can be a real pain. plus, if the move is too great, your perspective will change enough that you may never be able to match the background footage to the move.

at this point you could try to mimic the move with a 3d camera, positioning the background footage so that it seems like an appropriate distance from the foreground. or, just fake it, and keyframe movement of the background footage to create a believable motion paralax effect (it’s probably the easiest way). either way, if your camera movement is too great, you’ll start to run into problems.

Kevin Camp
Designer – KCPQ, KMYQ & KRCW

[Astonisher]

I think that having a moving shot in a car with a moving background will be very hard if not impossible to match up, especially if it’s multiple shots. What I would try and do is get a static shot of the car, and then get greenscreen footage of just the passanger/driver and then insert the street footage you took on one layer, with the static car shot on top of that and then a layer with the driver keyed out so the car doesn’t have much movement interior wise. But the person will be moving inside of it, assuming for instance if its like an over the shoulder shot with the car interior and then the person inside you’d be able to mask out the window for your background footage you’re bringing in and that should work fairly well. As far as movement goes if you took a few good pictures of the interior or of different parts, i.e. back of seat, dashboard, steering wheel, rear view windows and aligned them in 3d space correctly you’d be able to have realistic movement inside of the car with the passanger. It’s a tough one though, but maybe someone else can answer it better. Either way good luck and hopefully if the blue screen is yours you can try it out and experiment with different techniques.

Later,
Zack