I know that a Grey Card is used for the white balance of the camera, but whate are the Grey Balls used for?
On big Productions, there is usually a guy (what is his job?) that holds up a grey ball and a "mirror"-colored/reflective ball. What is this used for? Is this for digital effects added in post and to see the light and the direction of light? What is the purpose of them?
Also, sometimes, there is the use of a reference card (a paper with many little colored squares on there). What is that used for?
Is this to adjust the color of the digitally added material?
This can't be added to adjust the images in post, because they should be the same (because of white balance), is it? Does dynamic range matter with these kind of things?
What are these balls called and what for are they used? What Role/Job does the person holding them have? Does he has other duties or is he/her just holding them?