I was watching Pacific Rim Special Features disc last night. In one brief production scene, I saw a half moon shaped object which was chrome or mirror like. In another movie special features, I saw the same thing. It looked as though it was in the shape of a dumb bell, only with a thin rod between two half spheres. Just curious if someone could explain what this is and how it is used in production?
I believe you are referring to a chrome/gray ball rig. http://akromatic.com/gadgets-info/
This is photographed on set and then utilized by vfx look development and lighting departments in order to help facilitate the digital recreation of the lighting that was used on set. This is one step/tool used in an often complex process.
I'm a vfx lighting td ...so I just assumed that's what you're referring to. Much like a hammer assumes everything is a nail :)