From a paper by Jones in The Photographic Journal based on his Hurter & Driffield Memorial lecture. "Since that time the contributions of the theory and practice of tone reproduction have been many and varied. Much of this material has been summarized and analyzed by Dr Mees in his book The Theory of the Photographic Process, published in 1942. It is the intention of the present paper to pick up the story at approximately the point where it was left by Dr Mees in that publication... The general over-all theory of photographic tone reproduction has been discussed many times before and it is felt, therefore, that a greater contribution to this problem can be made only by dealing with it in a rather detailed fashion. To do this, the solution of an elaborated tone reproduction diagram, illustrated by a quantitative example, will be carried through."