Help Me Buy a… Telephoto lens

A telephoto lens is a key step in expanding your camera system

What they do and what to look for

Telephoto lenses magnify distant subjects so that you can still fill the frame when you can’t get close enough with your camera’s kit lens. They’re essential for sports and wildlife photographers, for example.

Telephoto lenses come in many different sizes; while many ‘amateur’ lenses are comparatively light and affordable, professional lenses can be extremely expensive. They also vary in their magnification, or focal length; the further away your subjects are from the camera, the longer the focal length you need.

Most telephoto lenses are zooms, which means you can easily adjust the magnification and adapt to different shooting distances, but some specialised and professional lenses are fixed-focal-length ‘prime’ lenses.

Choosing a telephoto is not necessarily straightforward, especially when you’re just starting out, which is where this guide

is designed to help. Once you know what you want to photograph and how much you’re prepared to spend, it’s a lot easier to choose the right telephoto lens for the job.

1 Telephoto types

Most people start out with a budget telephoto zoom, but you can also get more expensive ‘constant aperture’ telephotos, which give faster shutter speeds and shallower depth of field and are preferred by experts and pros. For super long-range subjects like birds and aircraft, you need a super-telephoto lens with a much longer focal length.

2 Full frame vs APS-C

With kit lenses and wide-angle lenses, you have to get a lens designed for your camera’s specific sensor size, such as APS-C or full-frame. With telephotos it’s different; if you have a Canon or Nikon DSLR, for example, a full-frame telephoto is the best choice because it will work on an APS-C camera too – and the 1.5x (non-Canon cameras) or 1.6x (Canon cameras) crop factor of the smaller sensor will give your telephoto lens more reach!

3 Maximum aperture

Most telephoto zooms have a maximum aperture that changes as you zoom in. This might appear in the specifications as ‘f/4-5.6’, for example. This means your shutter speeds will be slower at longer zoom settings, right where you really want them to be faster!

The aperture changes because maintaining a wide maximum aperture at long zoom settings needs a lot of very expensive glassware; so while ‘constantaperture’ zooms are desirable, they are heavy, often limited in their zoom range, and cost a great deal of money. For most users, a variable-aperture zoom is a better compromise in terms of weight and cost.

4 Image stabilisation

Some cameras have in-body stabilisation systems to help you get sharp shots, but most telephoto lenses have image stabilisation built into the lens. Some kind of stabilisation is essential for long-range photography, unless you’re using a tripod.

5 Weather sealing

It’s worth getting weather-sealed lenses, although a rain cover is the best solution for prolonged shooting in wet weather.

6 Focus limiters

Focusing can be a particular challenge with big telephoto lenses. Some makers offer a ‘focus limiter’ which restricts the close-focusing range of the lens and sets it to cover medium to long distances only. This can greatly speed up the focus response, because the lens is not trying to check such a wide focus range.