The dop (pronounced as letters: DOP or sometimes just dp) – director of photography – is responsible for the overall “look” of the film. They’re sometimes called the cinematographer.
They work closely with the director in determining that what the director sees in their mind’s eye is what finally appears on the screen.
Actors generally don’t have much to do with the dop but whatever else you do, they are always to be respected. Think of the dop as the director’s quieter and more thoughtful and wiser older brother who knows the mechanics of film making inside out.