Why it's essential to choose the right lens for the job

Award-winning wildlife photographer Will Clark reveals what’s hidden inside his camera bag

Camera body: Canon EOS 40d (1)

I've owned this lovely camera for a couple of years now, and hope to soon be moving up to the latest offering from Canon – the EOS 60D. I had bought the updated 50D but unfortunately it was ruined in an underwater accident before I got a chance to insure it.

Once you've bought a few lenses you find you stick with one manufacturer – my first DSLR was an EOS 20D so it has been a natural progression to buy from the evolving EOS range. The difference between top-end brands is actually quite small, although some people get very territorial and vocal about brand loyalties. Two of the main differences seem to be in the ergonomics of cameras and some technologies rolling-out from one brand sooner than another, such as HD video and enhanced low-light abilities.

There is an enormous range of lenses on the market that vary in price from being relatively cheap to mortgage-threateningly expensive. Choosing a lens involves comparing the price, the quality, the weight and the range of uses it will be put to. The quality of a lens is usually reflected in what it costs. Put simply: better lenses have superior glass inside sturdier bodies, which result in more sharpness, particularly in the corners of a shot, and more contrast – hence their better potential to produce clean, crisp and precise shots. Some lenses will autofocus much faster than others. Choosing a zoom lens over a prime (fixed focal length) lens gives you more flexibility, but this option can often mean sacrificing the maximum amount of light a lens is able to deliver to the sensor. Maximising this with wider apertures (lower "f" numbers) can be important for allowing fast shutter speeds to freeze the action in wildlife or sport photography, and when shooting in low-light situations.

Telephoto lens: Canon 100-400mm (2)

This large lens comes from Canon's L range, so it's made with especially superior optics and build quality. It zooms to 400mm, which is somewhat similar to the field of view that you would get from a pair of binoculars. On the downside it's a heavy lens to carry around all day. I use it for wildlife and candid shots, because you can shoot from quite far away from your subject. It is ideal for some sports photography, although the huge lenses that you see brandished by the snappers behind the goals on Match Of The Day are much bigger – and much more expensive.

Using telephoto lenses results in a very narrow depth of field – which refers to how much is in focus in front of and behind a subject before it becomes blurry. You can use this effect to make the subject of your photo really pop out, such as in portraits. A similar depth-of-field effect can be produced with shorter lenses by using wide apertures.

Extreme wide-angle lens: Tokina 10-17m (3)

Underwater photographers often use extremely wide-angle lenses known as fisheyes. These lenses let you get huge depths of field, but also result in a distorted, spherical view of the world. This might look strange in everyday images because they may didtort familiar lines, but underwater there are rarely any straight lines, so viewers don't notice the same distortion. That means I can get even crisper shots with massive depth of field from only a few centimetres away right back to infinity. This technique is known as "close focus wide angle".

Standard lens: Canon 17-85mm (4)

This was the lens that came with my first DSLR. It zooms across a range of angles from quite wide to quite narrow either side of what a human eye perceives, so you get a lot of framing choices. I find it useful for general situations, such as portraits, and when you can't predict what you might be shooting, such as for family outings, travelling or shooting in a club.

Macro lens: Canon 60mm Macro (5)

I use this lens for photographing subjects from around 30cm to only a few centimetres in size. Macro lenses are designed for extreme close-ups and also means you can get in really close. If you try using telephoto lenses to zoom in on little things through too much water, particularly if it is full of sediment, then the resulting photos come out all "wishy-washy" and indistinct.

Wide-angle lens: Canon 10-22mm (6)

This is probably my favourite lens: it is small, light and solidly built. It zooms through really wide angles of view. There's something about wide-angle shots that give them an artistic feel – you often see them used in photojournalism. When using these lenses it is easier to have really big depth of field, so in a crowd photograph, for example, everything from a person only a metre away to the far distance is in focus. At very wide angles, a slight distortion of the edges comes into play but in the right circumstances this adds to your shots, making them stand out from the usual.

This is my lens of choice for landscape photography as it is so wide, fitting in as much of the panorama as possible. I use it underwater, too, where you get the sharpest shots by minimising the amount of water between you and your subject. With wide-angle lenses you can get really close, still fit in your subject and also use the large depth of field to get everything sharply in focus.

Underwater Housing and Strobes (7)

I need to keep my camera dry when diving, so I use a special case known as a housing that allows access to almost all my camera's controls. Once you dive below a few metres the available light can be quite dim and blue, so you often need to add extra light using specialist flashguns – known as "strobes" – on the end of moveable arms connected to the housing. If you want to find out more, the best book I've found about using cameras while diving is The Underwater Photographer by Martin Edge, which has been recently updated.

Of course, the digital photography workflow doesn't end with the camera. Each shot has to be stored, assessed, labelled, categorised, enhanced and maybe shared or printed. I take an Apple laptop running Aperture on assignments to store and review my photos. I back-up my photos on compact USB hard-drives that I keep separately or post home in case of theft or loss.

A word of warning: there is no point in editing or printing your photos without managing the colour of your display and your printer – I use a gadget called an X-Rite ColorMunki for this. Finally, I either output to my website at willclarkphotos.com, upload to a client, or to my Canon 5200R printer.

The writer has just won the Beginner Portfolio award from The British Society of Underwater Photographers