Avengers 2 cross polarization camera + filter control
A fast but stable (vibration free) polarization angle switcher. The embedded microcontroller also fires the camera(s). By taking a continuous sequence of several shots, two that match closely can be culled.
Truth-be-told, I had about five hours to design and build this contraption before leaving LA for the Manhattan photo studio where the actors would converge the next day.
This allows diffuse and specular skin reference images without using a beam splitter (and thus halving of light intensity.)