Are you ready to shoot that bat?

The best photographic advice I ever received came from Terence Michael Shortt, the noted Canadian bird artist whose paintings my company published. He told me: "Decide on the composition of the picture within your rectangle and then forget about it. Concentrate only on capturing the drama of the eyes." This is exactly what I did when, with some trepidation, balancing myself on the bonnet of a Land Rover I directed my driver to steer straight at a pair of mating lions on the Serengeti Plains. The shot was my best wildlife shot, as the disturbed male glared at me with real hatred and peeled himself off his snarling mate.

Frank Greenaway, who has worked for 38 years in the Photographic Unit of the Natural History Museum in London, is best known for his extraordinarily dramatic photographs of bats. He has produced a lavishly illustrated handbook with vital information for photographers who want to improve their wildlife images, despite focusing more on the natural history behind the subject and the photographer's approach to it than on the technical aspects of photography. Photography itself, as Greenaway points out, "is best viewed as a technical pursuit blended with an artistic approach". The careful choice of equipment according to the type of nature being photographed, rather than solely for the equipment's ease of use, is a major part of success in nature photography. But the book does cover the technical basics of film and digital cameras, close-up work and elements of composition. There can be few photographers who will not learn from Greenaway's advice.

The advent of high-quality digital photography has been a godsend to the photographic industry. Today, it is not a good idea to buy a film-only camera, as it seems inevitable that film will rise in price rapidly as the mass market for it disappears. All my photography has been done on film, so I am a little sad to find Greenaway stating that the best aspect of the current 35mm film camera ranges is that with most of them one can buy a new digital body that will accept one's existing range of film camera lenses.

The maximum size of a sharp print made with a digital camera is governed by the number of data points (pixels) that make up the image. A small camera will have about four megapixels, while a large one has up to 22 megapixels.

The result is a staggering 4 million individual bits of information from smaller cameras and more than 20 million from medium-format ones. But the choice of a specific digital camera is still important: as Greenaway explains, matching a camera to a specialist interest (such as bats) is not too difficult, but finding a model suitable for the broad area of nature photography is tricky. His table of technical requirements for the major types of nature photography is particularly helpful.

The author also gives excellent advice on how to get the most out of compact digital cameras, which are increasingly popular with nature photographers because they avoid the complications or impossibility of re-shooting that occur with film. The correct specifications of lenses for nature photography-autofocus systems, aperture, depth of field and focal length are all discussed in detail, but in choosing a digital camera the prime consideration remains to decide on the chief purpose to which it will be put.

"Composition, style and collections", "Birds", "Mammals", "Reptiles", "Insects", "Water", "Plants" and "Habitats" each get a chapter, making for fascinating reading, with brilliant illustrations by the author. But his most important advice lies in the introduction to this invaluable book.

What is imperative for both the fledgling and the professional photographer is to understand his or her motivation. This preliminary self-examination requires absolute honesty. Once revealed, motivation can lead to a much more effective approach to taking pictures and, even more importantly, what to do with them afterwards. Just as lecturers have to understand their motivation in choosing photographs to illustrate specific points in a presentation, so must the wildlife author when choosing images for a book.

Finally, Greenaway stresses that observation and scientific understanding of the behaviour of target species must underpin serious nature photography. Know your animals and plants. Then it is possible not only to reach a new level of insight in nature photography but to experience the joy of a far deeper level of appreciation of the efforts of others.

Greenaway's lifetime of observation and study has produced one of the most illuminating wildlife photographic instruction books to be published in this new age of the camera.

Christopher Ondaatje is a trustee of the National Portrait Gallery and the author of several books containing his own photographs of African and Asian wildlife.