Give half a dozen men the same camera, lenses and plates, and send them to the same place to do the same thing, and all the results will be alike, or so nearly alike as to reveal the real mechanicalness of photography. Yet, curiously enough, this is just one of the most difficult things a photographer can be set to do, to exactly repeat himself, or another. He may use the identical apparatus, know the subject perfectly, and yet be totally unable to bring away an exact replica.
Frederick H. Evans