What marks out these photographs is hard to define. Some are clearly jokes - the incongruity of de Klerk in an animal pelt apron, or the normally spruce Clinton caught in slack, pink-skinned repose while smearing on sun cream. In other photographs, it isa matter of weird circumstances, a play of eccentric juxtapositions - the aeroplane that fell into the White House and crumpled itself into a statue of sorts, the posse of French politicians walking down a flooded street trying to look as if they were quite used to wandering thigh-deep in water while wearing suits...
But often, with the great iconographic photographs, the "big" pictures, what arrests our notice is not so easily summarised in words.
For here, we are moved quite simply by the strength of the image - that moment caught in the great tumult of the world.
Sometimes these photographs are taken in the normal run of news reporting - at a sporting event, or an election hustings, or perhaps a press conference. But more often than not the photograph represents life's most brutal extremes: disasters, earthquakes, famines and, in particular, war.
It is a language which seems to change little across the continents. That tumble of corpses in a skip, that man in rags lying on the ground with a gun to his temple... Are we in Angola? Rwanda? Haiti?
Yet, wherever these photographs come from, one thing is certain. The image, seen here in all its clarity and calm, will be quite unrepresentative of the chaotic, desperate circumstances under which it was taken. This is not, of course, to say that chaos and desperation may not be conveyed by photography, but rather that the very framing and freezing of the shot - starving baby to bottom right of the frame, vulture to the left - organises the heat and dust and noise of the street into something stiller and more purposeful. And this holds true even more when the photographer feels that he or she has caught that one moment - the expression on that woman's face, that camera angle, that happy configuration of the crowd - only by accident.
Anyone who has worked alongside a photo-grapher is likely, at some point, to have felt uneasy about this ordering of reality. We naively expect the photograph to authenticate our experience, to bear witness to what we have seen, but also to what we have heard and felt and smelt. And although, intellectually, we may acknowledge that photography is a subjective act - as much a personal editing of reality as any other human expression - it is still hard to dismiss the old belief that the camera "never lies'', that the photograph is always a transparent, unadulterated version of the truth, a clear window on to the real world.
Photographers have done their best to dispel this notion, knowing, as they must do, that television has become the primary news source and that, every year, the expansion of the international media machine, and the technical advances in computer-imaging,loosen their control over the final look of what they create.
As photographers rebel against these constraints, self-conscious use of strategies more usually associated with art photography creeps into photojournalism. The clean image is not enough. Watch for the highlighted warp of the lens, the inappropriate shutter speed, the still life of a soldier's boots or an incinerated helmet in the moonscapes of Kuwait.
Other photographers incorporate the circumstance of their work within the picture, and this makes for uncomfortable viewing. What are we to think of those sharpshooters in Port-au-Prince who circled round an injured man as if he were carrion? And, on page 18, the soldiers lying on the concrete - are they taking aim just for the benefit of the cameras? Are they shooting for the cameras?
For there is the rub - just as war accom-modates photographers, providing press passes and military escorts, so, inevitably, it draws them into the game. They, too, create the poses and propaganda. They, too, blur the edges; where, once, each war had itsown theatricals - the Crimea its moment of ghostly silence before the charge of the Light Brigade, Vietnam its formations of helicopters - now, thanks in part to the snappers, the lines begin to blur.
Take the photograph on this page. The young men of Chechnya go off to the front wearing Koranic scarves tied around their woolly hats. Where, you might ask, did they get the idea? Was it images in the press - the Iran-Iraq
conflict, or, more recently, Muslim guerrillas in former Yugoslavia - that encouraged this fashion? And was it those same images that spurred them on to fight in the first place? Where will we see that fashion next? On the catwalks of Paris, London, Milan...Reuse content