A beginner’s guide to interchangeable lenses for DSLR cameras. By Jac Kritzinger

Especially when you’re travelling, your choice of optics can mean the difference between getting exactly the postcard-perfect image you’re after and snapping something just so-so. A definite advantage of owning a DSLR is the variety of lenses available for these cameras, and thus the options available to you when you need to get a flawless pic.

But you can’t buy them all… Where to start? Try to borrow or hire the optic you are interested in and play around before committing. Try out different options and experiment in different conditions, and the right glass will soon find its way to your camera! In the meantime, these tips should point you in the right direction.

All about aperture

The first aspect you have to consider with any optic is the maximum aperture (how wide the internal mechanism can open to let light on to the imaging sensor). The largest is usually ƒ/1.4, while ƒ/2.8 is a general standard. The advantages of large maximum apertures are twofold: First, they are great for taking low-light photos, without having to revert to flash. Generally called ‘fast’ lenses, these optics let in more light, so that you can shoot at higher shutter speeds in surroundings with less light. Second, lenses with large apertures have a shallow depth of field – they throw everything in front of and behind your subject out of focus, fixing the eye on the desired centre of attention.

These lenses are great for shooting portraits of people and animals (both wild and domestic), as well as poorly lit interiors of buildings such as museums and churches when you’re out exploring.

Room for zoom

The most obvious optical choice among travellers is the zoom lens. It can cover a large focal range, often from as wide as 18 mm to as long as 300 mm in one package. While this is handy, one has to look closer at the specs – aperture is once again the key factor. Zoom lenses can be divided into two groups: fixed-maximum-aperture and varied-aperture. For example, a 24–70 mm ƒ/2.8 fixed-aperture zoom has the ability to stay wide open at ƒ/2.8 throughout the entire focal range. An 18–135 mm ƒ/3.5–5.6 varied-aperture lens can offer exactly what is specified: at 18 mm, the aperture is quite wide at ƒ/3.5; but, as you zoom to 35 mm, the aperture closes to ƒ/4; when you get to 135 mm, the maximum is set at ƒ/5.6.

If the obvious advantages of large apertures apply to you and your travels, a fixed-aperture zoom may be for you. They are, however, much bulkier and heavier than their cousins; they can also be very expensive. With varied-aperture lenses, you may lose out on low-light and portraiture capability, but there’s a much friendlier price tag, they’re lighter to carry around and manufacturers can cram in a much broader focal range.

Prime time

Fixed-focal-length lenses, or ‘primes’, can also be great travel companions. Without the bulk of zoom lenses, they offer very large maximum apertures and generally better image quality with fewer aberrations and distortions. The smallest, and most popular, are 16 mm fisheye, 24 mm, 35 mm, 50 mm and 85 mm. From there on up, both the sizes and the prices can very quickly become rather monstrous.

The obvious downside is that, as opposed to zooms, you have to carry more than one lens to cover a large focal range. Stick to the smaller stuff, though, and you may well find that a chopping-and-changing system works for you. New prime lenses can be a bit pricey, but, with exotic zooms being all the rage in the digital age, you should be able to find some great second-hand bargains if you take the time to shop around a little.

So, what lens?

Here are some lens recommendations to suit the most popular fields of photography when you’re out and about:

• Landscapes/architecture: 16–35 mm ƒ/4 zoom Great for a wide-angle view with minimum distortion and top image quality, relatively compact and generally fairly priced.

• Wildlife: 70–200 mm ƒ/2.8 zoom Nice coverage at the longer end of the focal range, especially when coupled with a 1.5× teleconverter. Offers exceptional quality. Quite bulky and expensive though.

• Street/inner-city: 50 mm ƒ/1.8 prime Large aperture, sharp, pretty cheap, zero distortion, small and unobtrusive. Also great for interiors and portraits, there’s very little the nifty 50 can’t handle.

• Close-up/macro: 60 mm ƒ/2.8 prime Good magnification, lightweight and also reasonably priced.

• Portraits: 85 mm ƒ/1.8 prime A classic portrait lens, affordable, fast and sharp. Light enough to sit on your camera all day. A 70–200 mm f/2.8 can also produce great portraits, if you can handle the bulk.

• General travel: 24–85 mm ƒ/3.5–4.5 or 24–105 mm ƒ/3.5–5.6 zoom Good all-in-ones covering broad focal ranges, relatively lightweight and won’t bust your budget. Not very fast or offering the best image quality, but you’ll get the shot.

Photography Gallo/Gettyimages, courtesy image

(This article was first published in the summer 2014/2015 issue of AA traveller magazine)