An expert from the book: Photography in Print: Writings from 1816 to the Present by Vicki Goldberg

If a photograph is to communicate its subject in all its intensity, the relationship of form must be rigorously established. Photography implies the recognition of a rhythm in the world of real things. What the eye does is to find and focus on the particular subject within the mass of reality; what the camera does is simply to register upon film the decision made by the eye. We look and perceive a photograph, as a painting, in its entirety and all in one glance. In a photograph, composition is the result of a simultaneous coalition, the organic coordination of elements seen by the eye. On e does not add composition as though it were an afterthought superimposed on the basic subject material, since it is impossible to separate content from form. Composition must have its own inevitability about it. – Henri Cartier-Bresson