Shooting green screen elements for perfect comp..

[RC23]

I'm about to shoot a small composition piece.

Let's say I'm shooting a street and want to comp in a giant robot (green screen element) into the street.. how do I figure out what the perfect angle to shoot the robot at is?
Without having a live view of course...

Is there some rule of thumb to work by?

Thanks

 

[Guy_Cochran]

Are you on a Mac ? Check out Veescope http://www.dvdxdv.com/NewFolderLookSite/VeeScope/Products/VeescopeLive.overview.htm

 

[k3pp]

1) Use some software to feed your composition with live video from the camera... maybe Frischluft´s Lensfeed
http://www.frischluft.com/lensfeed/lensfeed.php

2) Match the lighting of the background with de foreground....

I Think this will work...

 

[seejay1031]

As long as you use the same camera at the same focal length (the same lens, if on 35mm adaptor, crop factor should be the same too), you only need to match tilt, roll and height.

The tilt should be the same degrees in both cases, the roll is probably a non factor as your tripod was properly leveled prior to both shots, but if its a dutch angle you will have to match roll.
Height must be converted by scale. If you want the robot to be 1:10 scale and you took the street shot from a height of 6 feet. The green screen shot should be taken from a height of 7.2 inches (note that this is the nodal point you are measuring from). Chances are you will have to build a raised platform for the robot to make this possible. You will also need to shoot the robot in slow motion for it to look right.

I recommend picking up a copie of "The DV Rebel Guide" by Stu M. It explains this all in much more detail and even has calculators for determining this problem.