Rear projection is still a viable option, but as with VFX, if done poorly it looks ... bad. In the 30's & 40's audiences weren't bothered by poorly shot RP & obvious cut-away cars. Today, the audience (and the filmmaker) expect more.
There are many issues to tackle when shooting RP, and although the following list is by no means a how-to, here are some things to consider:
- Matching FG & BG key to fill ratio. Use a light meter & a green or blue viewing filter to help you judge this.
- Interactive Camera & Car movement.
- Steady BG photography
- Synching actor's 'driving' with BG
- Matching perceived speed difference between front and side shots (The 100/80/60% Rule is a good guideline)
- Planning coverage first so you can shoot BG element for projection.
- Camera movement limited to nodal pan/tilt.
- Exposure: If exposing for interior, the BG will want to be over exposed (or vice-versa).
- DOF: If you are focused on an actor in the car, the projected image may need to be blurred. This is a common mistake that screams 'Rear Projection' to the audience.
- BG image scaling to match the FOV used in the car photography. This also scream 'RP' if done incorrectly.
- Tilt: Horizon line between BG & FG.
- Match Camera Elevation between BG & FG
- Rear Projection hotspot.
- Color grading & Black point of BG
- Properly scaled exterior set pieces but introduce further DOF issues
- Splash light from the RP
- Test shoots are absolutely necessary.
- Shoot a few angles as possible, and sped your time getting it to look good.
Then, there's always green screen. This gives you the ability to mess with your FG/BG levels & colors within the composite. I usually choose GS over RP EXCEPT in one situation where there was rain running down the windows of the car, in that case I went with RP: Some SFX water on the glass, hit it with some e-Fans, and the water looked awesome. I still get some people arguing with me that it wasn't RP.
But if VFX is out of your skill set, and RP is too complicated, I recommend Poor-Man's Process , which is perhaps your best option if you need to get some simple night-driving shots, with good audio, in the safety of a stage environment; and you can move the camera!
Rok