Here is the confrontation young upstart Kubrick had with an established cinematographer re different focal lengths ,that Mercer is referring to.Kubrick is known as a "single camera director" but used multiple cameras sometimes like in the war room sequences of "Dr Strangelove.".He often shot a scene more than 30 times to reduce the artificial acting and get the performers displaying raw emotion.Not much use have fabulous cinematography if the acting is not up to it,the audio is poor or the story dull and boring.