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Guide to Lenses

Whether you’ve got an entry-level camera or a professional DSLR, your camera is nothing without a lens. Photography, by its very nature, requires light in order to generate an image, and your lens is the means by which your camera gathers that necessary light.

While contemporary compact digital cameras and ‘bridge’ or ‘superzoom’ cameras are improving their fixed optics all the time, a digital SLR offers you the option of choosing which lenses suit your individual shooting requirements, with an ever-increasing list of options unfolding.

A photographic lens is made up of several lens elements, arranged inside a barrel, that move in order to focus beams of light onto your digital camera’s sensor. A diaphragm – much like the iris in a human eye – grows larger or smaller according to the aperture that you set, and subsequently allows more or less light to reach the sensor. The performance of a lens depends largely on the type and quality of the components used in its construction. More expensive lenses include elements made from higher grade glass, while cheaper lenses comprise lower-grade materials. Pricier optics also tend to offer more advanced forms of technology, from silent motors and internal focusing mechanisms to gyros that combat camera shake and extra low-dispersion glass, producing sharper images with less distortion.

The focal length of a lens determines your angle of view – ie, how much of the scene will be recorded in a single frame – and the maximum aperture affects the light-gathering ability of the lens. Expressed as an ‘f-number’, the maximum aperture indicates how wide you can open up the diaphragm. A lens with a maximum aperture of f2.8 for example, is described as a ‘faster’ lens that can gather far more light than an equivalent lens with a maximum aperture of, say, f5.6.

Faster lenses are generally more expensive and produce higher quality, sharper images.
This guide aims to help you make a more informed decision when shopping for optics.

The basics
• Prime lenses have a fixed focal length and do not zoom. Because of this, they’re very well engineered, fast and produce high-quality images.

• Zoom lenses offer greater versatility and cut down the number of lenses you need to carry around, but they do tend to suffer more distortion than primes.

• Telephoto lenses are used widely by sports photographers and the paparazzi and as they enable the user to get close-up shots from a long distance.

• Wide-angle lenses are ideal for capturing vast scenes, from landscapes to panoramas and group shots.

• Generally, when shopping for optics, you get what you pay for. Lenses can be very expensive, but should stand the test of time and don’t depreciate in the same way as DSLR bodies do.

Prime versus Zoom
Prime lenses remain at a constant focal length, the ‘standard’ length being 50mm. They can be engineered with greater precision than zoom lenses, as the manufacturer only has to design them with one focal length in mind. Primes tend to have large maximum apertures, making them ‘fast’ lenses that are very efficient at light gathering. For this reason, this type of lens tends to be used by photographers who demand the crispest image quality.

Zoom lenses, on the other hand, are very versatile, covering a range of focal lengths. They are also a good option if you want to keep the weight of your kit bag down, or if you’re working in surroundings where it could be detrimental to your camera if you constantly have to change lenses – for example, in a dusty environment. The downside is that zoom lenses are slower than primes, offering smaller maximum apertures.

They also suffer more acutely from chromatic aberrations and distortion at some focal lengths, due to the complexity of the mechanisms required to shift the elements within the lens barrel along with the grade of the glass used to manufacture them.

When deciding whether to opt for a prime or zoom lens, you need to take into consideration what you’re going to be doing with your images and at what level. If you’re an enthusiast who wants to create some prints at home or enter some competitions for example, a good quality zoom lens from a reliable manufacturer can generate excellent results. If you’re a professional user, or you want to produce images of superior quality in order to sell them, then a prime lens might be worth considering instead.

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