How should our operators judge pad marks on polished collars?

I need an appearance check that our operators can repeat, because two people have given opposite verdicts on the polished collars from our FR10 gripper trial and both were looking honestly. One inspected beside the bench lamp and the other near the window. The supplier wants to try softer pads, which may help, but I don't want to call them successful simply because we changed where we looked. Who normally agrees the viewing conditions and the borderline samples, and how do you include that check without turning every transfer into a long argument?