Henri Cartier-Bresson [1908-2004] is the progenitor, and perhaps the ultimate personification of the photo-journalist in the 20th Century. Starting relatively late in life--following a period during which he flirted with painting, and later was seduced by the ideas of the French Surrealists--he roomed for a time with Robert Capa, and quickly became obsessed with the idea of capturing the frames of history-in-the-making, and he restlessly roamed the world with his neat little Leica 35 millimeter camera, concentrating on busy scenes of action, intersections, little human dramas, moments--as he would later (famously) be remembered for saying--in which the photographer might steal images from eternity. Another French photographer, Jacques Henri Lartigue [1894-1986], had shown, very early in the history of the medium, how action shots and candid (unposed) compositions and subjects could be as interesting as fixed, painterly arrangements. This "accidental" quality could be used to depict energetic gestures, odd, inexplicable juxtapositions, ironic contrasts, exotic details.
The candid, elusive moment of action or sudden gesture--passing quickly into oblivion--never to be retrieved--tantalized serious photojournalists, who hunted subject-matter, poised like gunslingers ready to pull the trigger at just the precise moment of meaningful action. Few worked as hard or as determinedly as Cartier-Bresson to seize such opportunities. Rather than the contemplative, staged canvases of large format photographers, the avatars of the new, portable cameras celebrated their facility to make innumerable frames by piling up hundreds, thousands of rolls of exposed film, hardly realizing, usually, what they might have caught in their pictures, until they developed the film, later, in the darkroom.
This procedure, in which thousands of images were built up to make a kind of cross-section file of a given session, enabled photographers to choose from among multiple views of a single situation. Rather than carefully framing a composition on the ground glass, photographers could review a host of images, choosing the best, and carefully cropping the individual images to heighten the effect--to, in effect, "compose" the picture after the fact.
One of the drawbacks of using small cameras, and high speed film, is the sacrifice of clarity and mid-range tones. Typically, 35 millimeter frames made from Tri-X high speed emulsion, pushed to absurd limits (setting as high as 2400 speed!) were all chalk and soot, with no subtlety or range. Pioneers of the medium usually figured out ways to overcome this limitation, but frequently their best images are a little rough, lacking depth of field, or sharpness (acuity).
The spirit of the new candid approach to image-making brought qualities not seen before: Humor, vicarious intrusion (and embarrassment), surprise, accident and jeopardy--in short, all the things which occur in life, but happen so unexpectedly or precipitously that there's hardly time to notice them, much less photograph them. This was the gambit of photojournalism, and the excitement and awe it inspired fascinated readers, viewers and gallery-goers for over half a century, and fueled the picture-magazine genre (Life, Look etc.) for decades.
The portability and lightness of the small cameras also made possible a liberating freedom of viewpoint, vantage, allowing photographers to enter intimately into scenes and situations where they could never have ventured before.
Viewers understood that all this candid drama was unscripted, which lent a certain vigor and vitality to the gambit. As the consciousness of the relationship between artist and subject developed, people began to play to the lens, opening a third dimension to the "secret" witnessing of the photo-journalist's presence. But from a purely aesthetic standpoint, the casual, unplanned spontaneity continued to be a valued aspect of the medium.
The theft of the dramatic instance/instant from time/history is like a scalp taken in the heat of battle. Gotcha! exclaims the shutter as it clicks, quicker than an eye can blink. Cartier-Bresson's masterpiece, the collection entitled The Decisive Moment [Simon & Schuster, 1952], with its luscious cover designed by Matisse, gathers 126 of his most successful images. Late in his long life, the photographer said this: "There is a creative fraction of a second when you are taking a picture. Your eye must see a composition or an expression that life itself offers you, and you must know with intuition when to click the camera. That is the moment the photographer is creative." This is the decisive moment.