Fundamental to mainstream photography is the process of finding situations which can be resolved into meaningful images. Some images, in controlled situations, can of course be constructed, first in the imagination, then by assembling, removing, and making other physical changes. But when the situation is outside the photographer's control as with street life in a city images are potential, unknown, waiting to be put together by that special interaction between observer and reality that makes photography unique in the visual arts.

Essential to an understanding of this process is the psychology of perception itself, and while there are different theories even today, the dominant ones derive largely from Hermann von Helmholtz (1821 1894). As explained by R. L. Gregory, they hold that the brain actively seeks to interpret the sensory input from the eye, and throws up hypotheses as to what is being represented. Now, photography takes perception a large step further to the creation of a permanent image. The photographer not only has to perceive accurately, but to try and make the perceptions "fit" a coherent image that he or she knows (or believes) will work.

As a photographer, you are essentially "hunting" for a photograph that meets your own creative needs yet is drawn from a fluid, evolving set of events. This is the essence of reportage, or photojournalism, and I want to begin with this, the most elusive and difficult area of photography, because to my mind it is one of the purest and most basic forms. Within much of...