Telephoto lenses prove invaluable when you can’t get near enough to the subject you’re photographing, as in most wildlife situations, where you don’t want to stress the animals but also don’t want to be eaten by a hungry leopard or stomped to death by an angry elephant.

It’s useful to think of telephoto lenses as telescopes for your digital SLR camera. Like a telescope, a telephoto lens enlarges your subject, bringing it closer and making it appear larger in your viewfinder and on your camera’s digital sensor.

The longer the focal length of a lens, the greater its magnification. Thus a 100mm telephoto lens gives twice the magnification of a 50mm standard lens, while a 400mm lens gives eight times (x8) the magnification of a standard lens.

If you’re on safari and there’s a big male lion staring at you from 50m away, he’s going to appear very small in the viewfinder with a 50mm lens on your digital SLR. Change that to a 500mm telephoto lens, and the lion is magnified 10 times. Now he nearly fills the frame and you can even see the scars on his face and the mesmerising golden eyes staring at you.

Prime v Zoom Telephoto Lenses

Telephoto lenses fall into two main categories:

1. Fixed focal length, or prime, telephotos
2. Zoom telephotos, offering variable focal length

1. Prime telephotos offer optimum image quality because they have fewer lens elements, meaning fewer compromises have to be made. Their main disadvantage is the fixed focal length, limiting your options when composing the picture.

When photographing fast moving subjects, as in a running antelope or charging rhino, you can find the subject suddenly looming too large in the viewfinder. Fixed focal length telephotos can also be large, heavy, and expensive.

They are nevertheless the first choice for professional wildlife photographers because the image quality can’t be bettered and they offer wider maximum apertures than zoom lenses of equivalent focal length.

This allows for shooting in low light conditions, which is often essential for professional wildlife photographers shooting early in the morning or late afternoon when the animals are most active and the light is softer and less harsh, but also less bright. This means you need a wide aperture if you want to use a fast enough shutter speed to freeze subject movement and eliminate any camera shake that is magnified when using long lenses.

2. Zoom telephotos are extremeley popular because of their versatility and often affordable cost. Lens technology has improved substantially in the past few years and today’s top-of-the-range zoom lenses compare favorably with prime lenses when it comes to image quality.

For all-round usefulness, combined with affordability and very acceptable image quality, telephoto zoom lenses make an excellent choice for wildlife photography as it’s a lot less expensive buying one zoom lens instead of two (or three) prime lenses to cover the same range of focal lengths.

Popular zoom telephoto lenses for wildlife photography include:
* Professional quality 70-200mm f/2.8 telephoto zooms - wide maximum apertures, but at a price
* 80-400 or 100-400 f/4.5-5.6 telephoto zooms - bigger zoom range, but slower lenses
* More affordable 70-300mm f/4.5-5.6 telephoto zooms - also slower, but mitigated by cost

Whether you opt for a more expensive prime telephoto lens or the versatility and affordability of a zoom, a telephoto lens is an abolute necessity for capturing exceptional and memorable wildlife images. See Canon telephoto lenses for more about the wide range of Canon lenses that can be used for wildlife photography.

If you’re a photographer using Canon gear and you intend selling your photos, then a Canon wide angle lens will prove an invaluable tool as the wide angle is arguably the most indispensable of all lenses.

In situations where a telephoto lens would be useful but you don’t have one, you can move closer to the subject or crop the image to fill the frame with your subject.

However, there is no comparable substitute for a wide angle lens. If you want your landscape to include foreground detail and distant mountains, you’ll have to move back a very long way to fit in the whole scene with a standard 50mm lens.

Similarly, when photographing tight interiors, there’s usually no space to move further back to include more of the scene, making it essential to use a wide angle lens.

If you use a Canon digital SLR camera such as one of the Canon Digital Rebels (Canon EOS 400D, 450D, 500D) or a Canon 40D or 50D, then it’s important to understand that these cameras are fitted with APS-C sensors that are smaller than a full-frame sensor. This has the effect of magnifying the image when using a normal Canon EF lens designed for use with 35mm cameras and is the same as using a 1.6x converter.

While this is great for photographers using telephoto lenses, it works against wide angle lenses, effectively making them longer - so your 24mm wide angle on a Digital Rebel becomes a 38mm (24 x 1.6) - almost standard rather than wide angle. To find out more about the impact of sensor size on a lens’s focal length, see Canon Digital SLR Crop Factor.