There are hundreds of lenses currently available across the major lens manufacturers, and if you look at older, secondhand examples you’re looking well into the thousands. So how do you go about choosing a lens for your needs?
Choosing a lens is a different game to choosing a camera, and it’s complicated by the fact that two lenses often appear the same on paper but vary in price considerably. For a lot of people, just the process of narrowing down the selection to a handful of options is stressful enough, particularly when you start to consider third-party options at a cheaper price. There is a logical way to make the right decision, though.
The first thing to work out is what will actually fit and work with your camera. Your camera’s manufacturer will have a range of options available and these may be split into full-frame and cropped-sensor (usually ‘APS-C’) offerings. Nikon, for example classifies full-frame and cropped-sensor lenses as FX and DX respectively, while Canon adopts the EF moniker for full-frame lenses and EF-S for those designed for its cropped-sensor bodies.
If you use a cropped-sensor DSLR you should be able to use full-frame lenses, although full-frame cameras are not always compatible with lenses designed for cropped sensors (and when they are there is a drop in effective sensor resolution, as the lens doesn’t quite cover the whole sensor). Check your camera’s manual as this may explain your options in more depth.
Focus on your focal length
It’s important to know how a lens behaves on your specific camera body as the size of its sensor can alter the effective focal length. A 50mm lens used on a full-frame DSLR will provide you with the field of view of a 50mm lens, although on a camera with an APS-C sensor using the same lens will result with an effective focal length of around 75-80mm. This is because the smaller sensor only uses the central part of the lens, effectively cropping away the edges and bringing you closer to your subject.
To work out the effective focal range of a lens when used on a non full-frame body, multiply the focal length(s) by the crop factor of your camera, which should be stated in its manual.
So, a 24-70mm lens used on a DSLR with a crop factor of 1.5x will produce an effective focal range of 36-105mm, meaning you lose your wideangle at the shorter end but gain a little extra at the longer end.
The maximum aperture(s) of your lens determines the extent to which a lens can admit light to the sensor at a given shutter speed. Prime lenses – ie those with only a single focal length – will offer one aperture, while zoom lenses will offer two to show the maximum aperture at each end of the zoom.
So, a prime lens may show an aperture of f/2.8 while a zoom lens may show an aperture of f/3.5-5.6. Some zoom lenses only bear one aperture, and this shows it can achieve the same maximum aperture at both ends of the lens, which is desirable. Whatever your lens, you can find its maximum aperture written after its focal length.
Maximum aperture plays a large part in determining the price of a lens; manufacturers will often carry two or three lenses in their line-ups with similar specifications, but with different apertures and very different price tags. The wider the maximum aperture the more expensive the lens is likely to be, although this also heavily depends on the focal length on the lens. In general, lenses closer to the 35-50mm range can offer wide maximum apertures such as f/1.8 and still be affordable, but as you get further away from this focal length, price increases. So, ultra wideangle lenses and super telephoto lenses with relatively wide apertures will be priced significantly higher than those with a more standard focal length.
Getting things stable
Some cameras have image stabilisation built into their bodies while others employ the technology in their lenses. If your camera lacks image stabilisation, you should consider a lens with the technology built into it, as this will help you to achieve sharper images at slower shutter speeds.
Most systems allow you to take images up to three of four times slower than you would otherwise be able to. To give an example, a 100mm lens on a full-frame body will generally allow you to use shutter speeds of around 1/100sec and higher – any slower than that and you may start to see some image blur. With image stabilisation, however, you may be able to use a shutter speed of around 1/12sec or even 1/6sec and still get sharp images. Bear in mind that image stabilisation doesn’t compensate for subject movement, only the movements created by you holding the camera. The exception to this is when panning a subject, where you can set the lens to a mode designed specifically for this for sharper results.
Image stabilisation can be found in a range of different lenses, but it’s particularly useful with longer focal lengths as images requires faster shutter speeds here to keep them sharp. When incorporated into wideangle lenses, such optics can be used to capture images at very slow shutter speeds, perhaps even 1/2 sec or less, making them great for street photography and low-light conditions. There will typically be a premium to pay over non-stabilised optics, so make sure to take this into account when comparing different lenses.
And if you fancy a change…
It is possible to use lenses designed for one system on a camera from another through the use of an adapter. Not every combination will work and the adapter will be an additional expense, but it’s a great way of using older lenses on newer bodies, ones you may have knocking around or ones you can find for bargain prices second hand. There may be some limitations with regards to autofocus or metering, and certain options you’re used to accessing may not be available, so check compatibility before you buy.
Will that be all?
The above should guide you through the basics but today’s lenses offer many further features you may want to consider. If you use a weather-resistant camera, for example, you may be interested in a lens with the same degree of protection, otherwise your setup won’t be completely weather-resistant. For longer, heavier lenses, check to see whether they come with a collar for mounting on a tripod as this will help you to mount it closer to the centre of gravity for your setup, and check whether a lens hood is included when buying wider lenses as this will help you to block out stray light when it’s sunny for better contrast and saturation in your images.
Types of lenses
Fixed Focal Length
Fixed lenses offer some advantages over zooms. They’re generally smaller and lighter, with wider maximum apertures and superior image quality. An ultra-fast (e.g. f/1.8) 50mm lens is perfect for low light, 85-105mm is ideal for portraits, while a fast 300mm (or longer) tele is a popular addition to any wildlife or sports shooter’s kit.
Most DSLRs come with a standard zoom; that is, one which spans the focal range from moderate wideangle to short telephoto. These ‘kit’ lenses are generally fine for most purposes, but there are alternatives that offer superior image quality and/or wider maximum apertures – at a price premium, of course.
Wideangles make subjects appear further away, enabling you to get more in the shot. Among the most popular wideangle zooms are the 10-20mm/12-24mm and 17-35mm ranges. Superwide lenses cause more distortion, especially when tilted off the perpendicular but, with care, can be used to inject drama into your photographs.
Telephotos make subjects appear closer. They’re ideal for sport and wildlife, where it’s more difficult to get as close as you’d like, while short teles are good for portraits. Telephotos increase the risk of camera shake, so consider one with Image Stabilisation if your camera doesn’t have it, or a wide maximum aperture.
Want a one-lens solution for your photography? Get a superzoom. While they rarely compare with shorter range lenses as far as image quality is concerned, an 18-200mm type lens offers the benefit of speed, convenience and a dust-free sensor. Good for general shooting at moderate print sizes.
Many lenses misleadingly feature the ‘macro’ moniker but a true dedicated macro lens lets you get close enough to reproduce your subject at life-size (or half life-size) on the sensor. Macro lenses (few of which zoom) come in a range of focal lengths, from standard to telephoto.
Most lenses have letters as part of their names. These usually denote what technology they feature and how sophisticated they are. For example, manufacturers who incorporate image stabilisation or low-dispersion elements in their lenses usually state this as part of the lens’s name. Other information gathered from these letters may be the type of mount the lens uses, whether any aspherical elements feature and whether the lens sits in the company’s ‘professional’ range, which can include weatherproofing and sturdier constructions.
Your easy guide to lens suffixes:
II/III – Denotes version of lens
APO – Apochromatic lens elements designed to produce sharper images by focusing all wavelengths of light to the same point
DG – Sigma’s designation for digital and full-frame lenses
Di – Tamron lenses designed for full-frame sensors
Di-II – Tamron lenses compatible with APS-C sensors
DO – Canon lenses featuring a diffractive optical element
DX – Nikon lenses designed for APS-C sensors
ED – Nikon lenses featuring Extra Low Dispersion element(s)
ED – Olympus and Leica lenses with low dispersion glass
EF – Canon lenses compatible with full-frame and APS-C-sized sensors
EF-S – Canon lenses compatible with APS-C sized sensors
EX – Sigma ‘excellent’ range of lenses
FE – Canon’s fisheye lenses
G – Nikon lenses without a manual aperture ring
HSM – Sigma lenses with Hypersonic Motor
IF – Internal focusing lenses
L – Canon ‘Luxury’ range of lenses
LD – Tamron lenses with Low Dispersion glass
MF – Manual-focusing-only lenses
OS – Sigma lenses with Optical Stabilisation
PRO – Tokina Professional range of lenses
TS-E – Canon’s ‘tilt and shift’ lenses
UD – Canon lenses with Ultra Low Dispersion element(s)
VR – Nikon lenses with Vibration Reduction
USM – Canon lenses with an Ultrasonic Motor