Photojournalism has its roots in the last century. There are thousands of photographs which convey the social and political history of everything from Irish people living in abject poverty to the American Civil War.

However, photojournalism as we think of it today - the photographer with his or her camera on the spot at the precise moment capturing a moment of significance - really only came into existence with the advent of the small camera, after the first World War. Before that, cameras were quite cumbersome, demanded a lot of time to set up and the participation of the subject - not very useful in the middle of a riot or some such situation.

The new technology meant there was more scope for photojournalism, and magazines such as Paris Match and Life, jam packed with photographs of the rich, famous and infamous, began to appear. In a publication like The Irish Times, photographs are generally used to illustrate articles, both features and those about news events. In general, pictures are used to make a page more visually appealing. How many are used and what size they are depends on the availability of space on any given day. It also depends on a publication's general policy. Some papers would be inclined to use more photographs than a broadsheet like The Irish Times - which because of its status as "the paper of record" tends to devote quite a bit of space to the written word.

Sometimes a photograph is used on its own - a stand-alone picture. It may be chosen instead of any text about a given story because the editor believes it will have more of an immediate impact. An example might be the famous picture taken by Eddie Adams, a photographer with the Associated Press. In this picture, Brigadier General Nguyen Ngoc Loan, who was then the South Vietnamese national police chief, is seen executing a Viet Cong prisoner on the street. To this day the photograph is a shocking depiction of man's inhumanity to man. While the photographer may only have been passing judgment on war in general, it is hard to look at it and not take sides - most people take the side of the unfortunate man having his brains blown out. On its own the picture tells a very clear truth, but perhaps not the full story; after all, scenes like this were taking place outside the camera's eye throughout the Vietnam War, with different victims and "executioners".

However, it is sometimes argued that photographs have lost their impact in today's world of visual overload. We see all sorts of astonishing things in the cinema and on television - humans morphing into alien beasts is a regular occurrence - and such an array of extraordinary things that photographers have to capture something quite remarkable to make us even take a look. We have also become increasingly jaded by real-life human misery. In fact, sometimes there is even outrage at the graphic depiction of a situation. A front-page colour photograph of war victims may be more likely to anger or alienate readers then to spur them on to protest against the cruelty of what they see. There are all sorts of ethical considerations with photojournalism. On the one hand, the news is supposed to be informative. But occasionally readers are offended by photographs which they feel are exploiting the subject. When is it right to use a picture of a child prostitute in Thailand?

Then there are the celebrity worshippers and the paparazzi. More and more magazines use photographs to show us such fascinating stuff as the colour of Mick Jagger's kitchen curtains - among them OK and Hello. There has always been an interest in the rich and famous, but with the rise of the paparazzi and the growth of this market, press photography may serve as nothing more than entertainment.

Press photography is dominated by men. On the staff of The Irish Times there are no women photographers; in fact, with a few exceptions women are largely invisible in press photography departments throughout the country. Why is it a man's world? And if there were more women, would the visual portrayal of the news be in any way different from what we see now?

See also `History through the camera's eye', on today's Arts page of The Irish Times.