Registering a car in 4 shots

[Spike Baumann]

Hi all,

I have to shoot a car thats going to be in 4 different shots from above on a jib with one night scene but the car is supposed to stay in the same exact spot in all 4 shots with it driving off in the last shot. My thought is to shoot the car in the last location and throw green fabric on the ground to key out and then just remove it for the last shot. People are going to be going in and out of the car for each shot. The last shot is at night also.

What are your thoughts or experiences on this?

 

[Chris Newman]

If I understand correctly, the car and camera aren't moving within each shot, and the 4 shots will be different locations and lighting.

With the car not moving in the frame, it is easy to rotoscope it, so no greenscreen necessary.

But, a better way would be to reframe each shot separately with the actual car in each shot. Get the position of the car as close as you can to correct, but frame it a bit wider than you want and crop/rotate in post so they match exactly. Using this method, you don't have to worry about the lighting and reflections not matching the locations. Just make sure the camera is in exactly the same position relative to the car (straight up X feet from the center of the roof, for example.)

 

[Shane Kelly]

I would:
1. use a prime lens
2. measure distance of jib/camera off ground
3. measure distance from film plane to spot on car
4. use an inclinometer for tilt of camera
match all of above.
5. get some clear plastic for monitor and draw outline of car on it so you can match shots.
6. shoot it slightly wider so you have room to reframe in post.

Shane.

 

[Chris Newman]

The inclinometer is a good idea, but it could get you into trouble if the ground (and therefore the car) is sloped differently in the different shots. To keep the camera in the same position relative to the car, you could measure from points at the four corners of the car to the camera, and match all of those between the four shots.

 

[Shane Kelly]

better idea from chris.
I would use the hight off the ground and distance to car as a starting point, though.

I wonder if some sort of multi laser pointer device would work. Keeping it in the same position when you move the camera would be the problem.

 

[Spike Baumann]

If I understand correctly, the car and camera aren't moving within each shot, and the 4 shots will be different locations and lighting.

Yeah but the location would actually be the same. Shoot the 3 shots that are supposed to be in other locations with the green fabric and composite new backgrounds or grounds for that matter and the last scene would actually be at the location its supposed to be at so it can drive off. I figured that if I did it that way the car would be in the same exact spot for all the locations and the light would change enough for each shot that it would look like different locations.

 

[Shane Kelly]

Ah, I didn't get that the car would be in one location. I'd say green is an option, then.
maybe hide some kinos under the car so you can get a clean outline for keying.

 

[Noah Kadner]

Hire a visual effects supervisor.

-Noah

 

[Clayton Harper]

This is really not that hard. You set the camera at the same height, angle, focal length, t-stop, etc. Shoot a little wide to allow for reframing. Spot meter to get similar levels (unless you are mixing day and night shots).

You are not going to pull keys on this footage. Hire someone to rotoscope the footage. If you are low on money, roto it yourself with Mocha AE and use a morphing tool for the transitions.

 

[Gavin Greenwalt]

Noah has the right idea.

Green is not your friend in this case. It won't work at all.

A car is a mirror. If you shoot a car in 3 different places it's going to look completely different in those 3 different locations. Lighting and Reflections will completely change the car. Shoot it in one location on green and you're going to have a green car that looks like it's in detroit while the background is paris. It'll look stupid. It'll also be all green on the sides. Which will look odd.

I would consider a motion control crane just so that you can ensure an extremely precise positioning. Then just align it down to the millimeter and you'll be all right.

If you can get a live feed off the camera and composite it over your previous shot. You can then adjust the camera a few millimeters to inches left/right/up/down as necessary.

In post you're going to want a compositor to roto out the car and use warpers to perfectly register the car. If you're within a few inches at 15 feet this should be seamless.

----

Alternately you could just use a CG Car.

 

[Jason Wingrove]

yes measurements (laser distance finder from ANY good 1st AC's kit) and inclinometers will get you 95% of the way

Then Video split operator with vision mixer ability to wipe / half mix your shots together on set LIVE
SO helpful to be able to line up comparing to a before/after image, wiping or mixing on the monitor right in front of you. do it this way or be ready for pain later on.

worst case would be taking footage into photoshop or FCP to do the same but doing it against live footage means you can directly correct your framing, height, cam pos etc .. THEN youve got it close enough that even the worst post house couldnt screw it

jason

 

[Noah Kadner]

Yeah in the big boy world the car would be CG and you'd just shoot background plates.

Noah

 

[Spike Baumann]

Yeah the CG way would be best but they are trying this with a small budget. I will look into the live mixing since that seems like the best way to register. Motion control crane is out of the question. Thanks for the input.

Spike