Cross-polarization with multiple lights, multiple cameras on large objects in 360

Question

I'm trying to utilize cross-polarization to eliminate reflections on objects. I use linear polarizing filters on multiple light sources (polarized lights are my only light sources, no bounce lights) and a circular polarizer filter (CPL) on the camera lens to achieve cross-polarization. The object is on a turntable so I can shoot 360 photos without moving the camera around.

I'm using Canon EOS 5D Mark IV, 24-105 mm & 16-35 mm zoom lenses, with 4+ 1000W tungsten lights. I'm currently at the testing phase, I will eventually scale the whole setting up for objects as large as 10 feet wide.

I've lined everything perfectly so there are no reflection on even somewhat glossy objects. After that I start to move the camera on the vertical plane (up and down) and tilting the aim angle to aim at the object, I don't move the lights, only the camera.

Here are the issues I ran into when I do so:

1. When I changed the camera heights, I lost the cross-polarization. If I rotate the CPL, it will only get some lights into the cross-polarization, not all of them. I thought the polarization will offset by the same amount when viewing from different angle, but it seems they are offset by different amount.
2. When I start to rotate the object on a turntable (it is not perfectly centered, so it will rotate off the vertical axis ), I lose cross-polarization on some lights, which light to lose the cross-polarization depending on the rotation of the subject.

I would like to know how the above happen and how to solve these issues. Also, any practical suggestions on how to do a larger version (10 feet wide) of the setup while still maintaining cross-polarization across the subject, preferably with multiple light sources & multiple cameras (angles)?

Thanks in advance!

Answer 1

Anytime you move the camera, the angles between each light, the subject, and the camera will change by differing amounts. Thus the filters on the lights must each be adjusted to compensate for the different angles.