Dslr Lens tips

SLR Tips Lens buying guide

The joy of owning a DSLR is the ability to change lenses. You could go for a wide angle to squeeze more in, or a telephoto to magnify a distant subject. Or how about a macro lens for taking great quality close-ups? There’s almost no limit to what you can do, with lenses to suit all occasions – and budgets – but so where do you start? In this guide we’ll explain everything you need to know about buying lenses and help you make the right choice for your style of photography.

When choosing a new lens for your DSLR, you should think about what kind of photos you’re trying to take how and you’re finding your current model unsatisfactory. Maybe you’re struggling to fit everything in. Perhaps you can’t get close enough to sports players or wildlife. Or you might be perfectly happy with the range of your current lens, but you fancy something which delivers better quality, focuses quicker, has anti-shake facilities or maybe works better in low light.

There’s almost always more than one lens which does what you’re after, so the next step is working your way through the options which are available. If this is your first DSLR, the names given to lenses can often feature a bewildering array of letters and numbers, but it’s actually easier to decipher than it first appears. Here are the key specifications to look out for.

Focal length

The most important lens specification is the focal length. This defines the coverage of the lens, and how much you’ll fit into the photo. Focal length is measured in mm, and the number which closest matches the magnification of the human eye is 50mm. Our eyes have a much bigger field of view, but if you were to look at something in person, and then through a 50mm lens, the actual magnification would be similar. This is why 50mm lenses are known as standard lenses – they’re suited to a wide variety of subjects from landscapes to portraits.

Lenses with focal lengths smaller than 50mm are known as wide angle because they fit more into your photo. If you’re stood in the same position, a 25mm lens will have twice the diagonal field of view of a 50mm, and could therefore be used to squeeze in large buildings, landscapes or even big group shots – ideal when you can’t step back any further. 28mm is the most common wide angle focal length and is ideal for landscape and architecture shots, but you can go much wider still if desired, and anything below 20mm is typically known as an ultra-wide angle lens.

Squeezing in such a big view means wide angle lenses inevitably suffer from some distortion, especially towards the edges, but this can be used to exaggerate subjects for a special effect; indeed a special type of ultra-wide angle lens called a fish-eye deliberately uses distortion to deliver a highly curved result. Lenses with shorter focal lengths also inherently have a larger depth-of-field, which means it’s easier to get lots in focus from near to far. The examples here were taken with a 17mm focal length.

Lenses with focal lengths bigger than 50mm are commonly known as telephoto models. These fit less in, and are therefore ideal for getting closer to distant subjects or picking out detail; they also give a more flattering effect when taking photos of people. In contrast to wide angle, lenses with longer focal lengths have an inherently smaller depth of field, which means it’s easier to get a blurred background effect – again ideal for portrait, wildlife and sports photography.

Good focal lengths for portraits are typically between 85mm and 135mm – these are often known as short telephotos. Appropriate focal lengths for sports or wildlife are generally much longer – at least 200mm, and ideally 300mm or more. Professional sports and wildlife photographers often use 600mm lenses, or even longer still. The two examples here were taken at 400mm.

You can buy lenses with either a fixed focal length which doesn’t vary, or a zoom lens which goes from one focal length to another. Zooms are very convenient, but generally aren’t as good quality as a fixed lens. Fixed focal length or 'prime' lenses are also normally smaller, lighter and give a brighter view that’s better for low light – see aperture section on the next page. It’s all about weighing up convenience against quality, although some more expensive zooms can be very good.

General purpose zooms usually go from wide angle to short telephoto, such as 28-80mm, although some ‘super-zooms’ could give a range from 28-300mm, covering almost every photo opportunity. There are also wide angle zooms which normally offer an ultra-wide to normal range, such as 16-35mm. Similarly there are telephoto zooms which go from short to long telephoto focal lengths, such as 70-300mm.

Next we'll look at what you'll get in practice at different focal lengths and find out about lens brightness in our coverage and aperture section.