Shooting a car over green screen

[Zhibo Lai]

We'll be doing some green screen test behind a car to composite in a moving background. We'll shoot background plates of a forest road, and add in reflections in post.

Was wondering if anyone has any experience in lighting and shooting for this, and placement of the green screen in relation to the car.

We'll have 4 actors in the car, they're driving it, but for the green screen, they'll be stationary of course. We're planning on shooting outside, in a parking lot, to match the natural sunlight.

Shooting on Red, compositing in AE.

 

[Chris Newman]

We'll be doing some green screen test behind a car to composite in a moving background. We'll shoot background plates of a forest road, and add in reflections in post.

Was wondering if anyone has any experience in lighting and shooting for this, and placement of the green screen in relation to the car.

We'll have 4 actors in the car, they're driving it, but for the green screen, they'll be stationary of course. We're planning on shooting outside, in a parking lot, to match the natural sunlight.

Shooting on Red, compositing in AE.

I'd say don't expect to get any decent shots that show the outside of the car unless you have a very large visual effects budget. Here are some reasons:
- The car will reflect the green in an unusable way.
- Adding realistic reflections of the forest that follow the contours of the car would be very difficult.
- Adding shadows that a real forest would cast across the car as it moves would be very difficult.

Green screen for backgrounds behind the actors inside should work though.

 

[Reinhold R.]

I'd say don't expect to get any decent shots that show the outside of the car unless you have a very large visual effects budget. Here are some reasons:
- The car will reflect the green in an unusable way.
- Adding realistic reflections of the forest that follow the contours of the car would be very difficult.
- Adding shadows that a real forest would cast across the car as it moves would be very difficult.

Green screen for backgrounds behind the actors inside should work though.

I have to agree with Chris. Using a green screen in this case would cause you more problems than benefits. Placing a screen behind the rear window just for the actors would make sense though. If you already know the lighting situation the road will later be in, it would help if you mimicked it as closely as possible when filming the car. Re-lighting in post is extremely hard and hardly ever looks convincing.
For the reflections I would advise you to grab two extra cameras (cheap HD cams would do) and use them to film out of either side of the car when you go filming the road sequence. You can use that footage in combination with the background plate to render the reflections using a CG model of the car.

 

[Zhibo Lai]

We're only shooting car interiors over the green screen, primary for the shots that are too difficult/costly to shoot in post (looking through the front windshield). The exterior car shots, we're doing on location.

So we're mostly green screening the back window, and would need to add reflections into the side windows.

 

[Chris Newman]

You will still have a problem with no moving shadows in the interior, so I would stage it (and film the exterior and plates) where there aren't tall trees casting shadows on the car.

When shooting the green screen shots, keep the direct sunlight off of the green screen, otherwise it will be much brighter than the subjects and cause a lot of spill.

 

[Zhibo Lai]

Thanks for the tips. We completed our first test last Sunday. Ended up hauling half the car into a garage and duvetined the roof to kill the front windshield reflections. The harsh sunlight on the green screen was a big problem, along with the constant temperature shifts and blowing winds. Our reflection plates were a bit off and need to be shot better to match angle and motion of the background plates.

We're sticking with straight flat roads, with no overhanging trees to kill off shadows and matching the spin of the steering wheel with the curve of the road.

We'll prob end up shooting the whole setup in a big garage and kill off all sunlight.

 

[Noah Kadner]

It's not too hard to fake moving shadows actually- just grab tree branches, cucolorises and blocks of wood. Have spotlights at varying distances on either side of the car and then a few folks on ladders waving them past the lights at random intervals. You'd be surprised how well it sells, especially in short takes. A lot of movies fake car shots. Just about every scene in a vehicle on 24 is shot on a stage, though they use rear projection which makes things a lot easier than green screen in terms of reflections. Also on long lenses so the BG goes naturally out of focus.

Noah