Digital SLR: How to buy the best digital SLR Buying digital SLR lenses

Fit a good-quality lens to your digital SLR camera and you should get better results

Our expert Which? reviews of the best digital SLRs are based on each camera's performance with its packaged kit lens.

Generally, the results far outweigh what you can achieve with a compact digital camera. However, these cheap kit lenses only scratch the surface of what you can achieve with a digital SLR.

By attaching more expensive specialised lenses, a digital SLR really comes into its own, delivering stunning picture quality that surpasses the results you'll get with any basic kit lens.

Which digital SLR lenses to buy

Lenses for digital SLR cameras come in many different sizes and types.

Fixed focal-length lenses

Fixed focal-length lenses can give you better image quality, but offer no zoom range – you'll have to stand closer or further away from your subject, or else zoom and crop the photo digitally. 

One key advantage of fixed focal-length lenses is that they allow for much larger aperture values, letting you take brighter pictures in low light and creating blurring background effects.

Telephoto superzoom lenses

Telephoto lenses are a popular choice for people upgrading from their basic DSLR kit lenses. A superzoom lens will let you get much closer to more distant subjects.

It's often useful to seek out a telephoto zoom lens with a built-in image stabiliser, as trembling hand motions tend to be exaggerated in zoom conditions.

Macro lenses

You can also buy macro lenses for better extreme close-up photos, for example butterfly-on-a-flower type shots.

Macro lenses are commonly fixed focal length, though it's possible to find macro lenses with small zoom ranges as well.

Wide-angle lenses

If you're keen on landscape photography, consider a wide-angle lens. There are lenses available with wide angles of 12mm, 11mm and even 10mm. These lenses allow you to fit a huge amount into your shots – great for capturing landscapes, tall buildings, or indoor shots when there's not much space to stand further back.

To see a wide-angle DSLR lens in action, see our hands-on video with the Canon EF-S 10-22mm wide angle lens:

Checking digital SLR lens compatibility

Always be aware of potential incompatibility between lenses and digital SLR cameras. For example, Canon lenses fit only Canon digital SLR cameras and Nikon lenses fit only Nikon digital SLR cameras.

When you buy a lens made by a third-party manufacturer, such as Tamron, Tokina or Sigma, you should specify the make of your digital SLR camera to ensure the fitting is correct. 

Buying used digital SLR lenses

Used lenses can sometimes be very good value – you can even use older lenses from film SLRs. However, always check that any used lens you're thinking of buying is fully compatible with your digital SLR camera.

The focal length on the lens is not the same as you'll get with your digital SLR

Focal lengths on digital SLR camera lenses

Unless you own a top-end digital SLR camera costing thousands of pounds, the stated zoom range on any lens is normally not the zoom range you get when you use it on your digital SLR camera.

For example, the Canon 18-55mm lens has an optical zoom range of 18-55mm. This is the zoom range you would get if you fitted this lens to a film SLR.

The first number on any zoom range shows the angle of view – the lower the number, the more you can zoom out. The second number shows how far the zoom extends – the bigger the number, the further you can zoom in.

However, when you fit this 18-55mm lens to the Canon EOS 500D DSLR, say, the zoom range becomes 29-88mm because of this camera’s internal design. This optical zoom range change is sometimes called focal-length multiplication, or 'crop factor'. 

In the Canon EOS 500D's case, the focal-length multiplier is 1.6x. The actual, real-life zoom ranges of all lenses (for example 18-55, 100-300mm and so on) are subject to a multiplication of 1.6. Other camera systems can have focal-length multiplications of 1.5x or even 2x.

Full-frame digital SLRs

Only very expensive full-frame digital SLRs, such as the Nikon D700 or the Sony alpha 900, have no focal length multiplication. If you attach an 18-55mm lens to one of these cameras, you'll get a focal length of exactly 18-55mm. This can be particularly advantageous with wide-angle photography.

A good image stabiliser can help reduce blurring

Digital SLR lenses with image stabilisation

Some digital SLR lenses have built-in image stabilisers. These are often labelled IS (image stabilisation), VR (vibration reduction) or OS (optical stabilisation), and tend to be more expensive than lenses without stabilisers.

These lenses have a small mechanical element that detects trembling hand movements and compensates with a corresponding motion of its own. 

Generally, the image stabilisers found in digital SLR lenses are far more effective than the small ones found in compact digital cameras.

An image stabiliser tends to be most useful when you're photographing in low light, and need a longer shutter speed in order to capture your subject. The longer your shutter speed, the more likely you are to see blurry footage, so a good image stabiliser can really help in such conditions.

Image stabilisers can also be useful with telephoto zoom lenses, as even small trembling hand movements can be exaggerated by the zoom lens.

Some digital SLRs have image stabilisers built directly in to the body of the camera itself. These work by shifting the sensor when motion is detected. An advantage of this is that you won't need to buy lenses with stabilisers, which can save money on future lens purchases.

More depth of field means more of your picture will be in focus

Aperture and depth of field

All lenses have an aperture (a little hole), through which light passes to create the photograph. Changing the size of the aperture can give different amounts of ‘depth of field’. Depth of field is the distance in front of and behind the subject that is in focus.

More depth of field means that more of your picture is in focus. Little depth of field can mean a blurred background in a photo, and is a useful technique for pleasing portrait shots.

Consider an example of a photo of a person standing in front of a field of donkeys. With lots of depth of field, the person and the field of donkeys will both be in sharp focus. With little depth of field, just the person will be in sharp focus and the field of donkeys will be blurred.

The size of the aperture is represented by the f-stop. The smaller the f-stop, the bigger the aperture and the less depth of field you have – f1.8 and f1.4 are examples of particularly small f-stops, though you'll only encounter such large apertures on fixed focal-length lenses with no zooms.

You usually change the aperture size using the digital SLR camera’s controls, though each lens has a maximum and a minimum aperture size (and corresponding minimum and maximum f-stop) which the camera automatically detects.

Little depth of field means more of your photo will be blurry

More on f-stops on digital SLR camera lenses

The 'maximum' aperture of a lens, in other words how big the aperture can get, is usually stated on the lens. The bigger the aperture (in other words, the smaller the f-stop), the more light can get on to the digital SLR sensor.

This means shutter speeds can be shorter, reducing the chance of blur. This is in addition to less depth of field.

Lenses usually have their maximum apertures stated as a range, as the maximum aperture is different at different ends of the zoom. Remember the size of the aperture is represented by the f-stop.

For example, the Canon EF-S 18-55mm f3.5-5.6 has a maximum aperture range of f3.5-5.6, where f3.5 is the maximum aperture at the zoomed-out end of the lens, and f5.6 is the maximum aperture at the zoomed-in end of the lens.

Autofocus (AF)/Manual focus (MF)

Virtually all digital SLR lenses offer auto-focusing – but always check they're compatible with your digital SLR camera's autofocus (AF) system. If you're using an older lens from a film SLR, which may fit a digital SLR from the same manufacturer, you may find the AF systems are incompatible.

All lenses offer a manual focusing (MF) mode too if you prefer – simply flick a switch on the lens body to alternate between AF and MF.

In low light, the autofocus can sometimes take longer to find its subject. In these situations, it can be handy to rely on manual focusing – provided you can make out the subject by eye.

It can also be useful to use the manual focus when you're anticipating a fast-moving subject. At a race track, for example, it's handy to set the correct focus before your subjects start passing by at high speed.

Weight and length of digital SLR camera lenses

Most basic kit lenses weigh between 200 and 500 grams. Add a heavy lens to your digital SLR camera and you could have quite a heavy package to carry around with you. It’s always worth considering the weight and dimensions of a lens before buying.

Zoom lenses can, of course, replace the need for carrying around many fixed focal-length lenses. However, their performance at any specific focal length within their zoom range typically won't be quite as good as what you'll get from an equivalent fixed focal-length lens.

Filters can be added to the lens of your digital SLR

Adding filters to your digital SLR lenses

Filters can be added to your lens, and there are lots you can buy.

For example, a polarising filter can make the blue of sky in your pictures more intense. A starburst (sometimes also called 'cross star’) filter can create 'star' effects from light sources such as candles or lightbulbs.

A UV/skylight filter can absorb UV haze in sunny landscape pictures. Since this is the only effect it has, it's a good filter to leave on as it offers protection to the glass of your actual lens.

Many effects that filters create can also be done using image-editing software on the computer, but having filters can help the photographer to better visualise the image, and can also save time in the long run.

Finally, make sure you buy the correct size filter for your lens.