back projection using video projectors
 

Hi,
Has anyone tried setting up back projection using a video projector? I want to do the classic "actor sitting in the back of a car with the road disappearing behind him" shot, and I'm reluctant to do greenscreen as I am going for a very shallow depth of field with some handheld movement. Any ideas/suggestions would be useful

I don't see any reason why it wouldn't work. Somewhere there's a thread around here about people doing this... I had to film a little sequence with a model helicopter and I did it in front of my plasma screen instead of compositing it. Looked fine.

But I just read a big article somewhere recently (maybe American Cinematographer?) about how Hollywood is using digital projection for this a lot now with the advent of higher resolution projectors.

You shouldn't have too many difficulties with that shot, although you'll need to make sure your video projector is powerful enough and you've got a large enough studio for the throw. You'll want to avoid having a hot spot in the centre of the screen, so you may want to use a longer focal length projection lens. Also, ensure your screen is big enough for your planned shot: if you're shooting handheld, wide angle lenses show a lot of background.

If it's a daylight scene, I'd expect you'll find the problem will be flagging the stray light from the back projection scene.

http://www.cinematography.net/Pages%...ectedImage.htm

It would be a good idea to do a test first.

You could also try running the projector slightly out of focus. That will give you the shallower depth you're looking for, as well increasing the perceived resolution of the projection, because you won't pick up the individual pixels. :)

Here's something that may work. Using a super wide angle lens and/or fish-eye type of effect, you can make the image bulge in the center. Then using a projection screen that you can wrap, project into it maybe from above the car aimed down and adjusted for trapezoidal effects. Then you might get a wider looking world behind the car, and if you change camera shooting angles, it may give more depth to the background.

You could also try using the projector to project blue or green, which would be more even than a blue or green screen.

Eric