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How to buy the best camera lens for your SLR or compact camera

Got an SLR or CSC and still using the kit lens? We reveal what a lens upgrade can do for your photography

If you have more than a passing interest in photography, the chances are that you own an SLR or compact system camera (CSC). They offer lots of benefits over a smartphone: comfortable ergonomics, tactile controls, a large viewfinder, superior performance and a big hike in image quality.

They also offer the ability to switch lenses. While it’s handy to have a lens that does everything, it’s even better to have a lens that excels at the specific photographic challenge you’re currently working on.

A typical kit lens is pretty unadventurous, with a 3x zoom and a not particularly bright f/3.5-5.6 maximum aperture. Other lenses cover all sorts of specialisms: wide-angle, telephoto, macro, wide-aperture, tilt and shift, fisheye. Some include stabilisation; some are built for compactness; some cover a big zoom range; and others can’t zoom at all. Their prices range from £80 to £15,000 and beyond.

Building up a collection of lenses can be expensive, but lenses keep their value much better than camera bodies, and you can continue using them when you come to upgrade your camera. In this article, we’ll explore what’s available, what the various types of lenses can do and how much you might need to spend. If you’re still using your camera’s kit lens, we’ll help you make your first upgrade to start unlocking the true potential of your camera.

How to buy the right lens for your camera

The first step is to make sure you choose a lens that works with your camera as they need to fit together physically, and that’s dictated by the type of lens mount used. There are mount adapters that, in some cases, allow you to mix and match, but unless you have very specific needs, it’s best to stick to the same mount for camera and lens.

SLR lenses are available for Canon, Nikon, Pentax and Sony cameras, and each uses its own mount. To help distinguish these SLR mounts from other mounts from the same companies, they each have a specific name: Canon EF, Nikon F, Pentax K and Sony A or Alpha. The Sony A mount is actually the same as the Minolta A mount; Sony bought Minolta and adopted its lens mount when it launched its first SLRs back in 2006. That might be useful to know if you’re on the hunt for second-hand bargains.

Just because a lens fits on your camera, it doesn’t necessarily mean it’ll work. For example, Canon uses the same EF mount for its full-frame and cropped-sensor SLRs. A cropped sensor is smaller than full-frame, and so any lens that’s designed for full-frame will work perfectly well on a cropped-sensor SLR, too. It will focus light beyond the edges of the sensor, but there’s no harm in that. However, a lens that’s designed only for cropped-sensor SLRs won’t be able to create an image that fills a full-frame sensor. Some full-frame cameras recognise these lenses and will automatically switch to cropped-sensor mode, but that defeats the purpose of buying a full-frame camera.

The upside for cropped-sensor SLR owners is that these lenses tend to cost less than their full-frame equivalents. SLR lenses designed for cropped sensors are identified in different ways. Canon calls them EF-S mount. Nikon uses FX for full-frame and DX for cropped-sensor. Sony’s cropped-sensor SLR lenses have a DT prefix. Pentax full-frame lenses are known as FA, while its cropped-sensor lenses are called DA.

A guide to buying the best mount for your SLR or compact camera

SLR camera mounts have been around for decades and have evolved over that time. For example, the Nikon F mount was launched in 1959, and since then various electrical contacts have been added to control focus and aperture. In most cases, the cameras and lenses are forwards and backwards compatible, so they’ll be usable but might miss some features if the camera or lens doesn’t support it. However, some old lenses may not work or may even damage the camera, so do your research before shopping.

The most common pitfall is that recent Nikon lenses have an integrated autofocus motor, and so various consumer-oriented Nikon SLRs (the D3400, D5600 and their predecessors) omit the in-camera autofocus motor required to drive older lenses. Lenses designated AF-S, AF-I or AF-P will be fine, but others won’t offer autofocus on these cameras. This includes the Nikon 50mm f1.8 D AF, which costs around £160, so you’ll have to go for the more recent Nikon 50mm f1.8 G AF-S (approx £200) instead. Pricier Nikon SLRs such as the D7500 and its predecessors don’t have this issue.

Compact system cameras, also known as mirrorless cameras, are relatively new and so there are fewer compatibility issues to navigate. Most manufacturers have their own mirrorless mount: Canon EF-M, Nikon 1, Fujifilm X and Pentax Q. Sony has two versions of its E mount: lenses called Sony E are for its cropped-sensor mirrorless cameras, whereas you’ll need Sony FE lenses for its full-frame mirrorless cameras.

Olympus and Panasonic collaborated to produce the first mirrorless mount, known as Micro Four Thirds (M43), and you can mix and match their cameras and lenses. The only proviso is that all Olympus M43 cameras include in-body optical stabilisation. As a result, very few of Olympus’s lenses have stabilisation built in, whereas Panasonic has tended to include stabilisation in its lenses and less often builds it into its cameras. As a result, combining a Panasonic camera and Olympus lens may leave you without stabilisation.

There are various other manufacturers that produce lenses for a range of mounts: Tamron and Sigma are the two big names, but there are various others such as Samyang, Tokina and Voigtlander. Tamron and Sigma tend to be a little cheaper than buying a similar lens from Canon, Nikon and so on, and they’re generally up to scratch for image quality.

All you need to know about aperture, focal length, depth of field and zoom

Lens names are usually a pile of letters and numbers. They’re not the catchiest of names but, once you understand the jargon, it gives you a good idea of what’s on offer. Let’s take the Canon EF-S 18-135mm f3.5-5.6 IS USM as an example. We know it’s made by Canon, and EF-S tells us that it works with Canon SLRs with a cropped sensor.

The 18-135mm figure is the focal length range. This dictates the zoom position of a given lens, but whereas a 7.5x zoom only tells you how big the range is, an 18-135mm focal length range tells you the specific zoom positions offered by that lens. 18-55mm and 100-300mm both have a 3x zoom, but they’re very different lenses. 18-55mm is relatively wide-angle, whereas 100-300mm is a telephoto lens.

The focal length can be converted into a horizontal field of view (FOV), which is the angle from the views that make up the left and right edges of the frame. For example, an 18mm focal length gives a 90-degree horizontal field of view. As the focal length gets longer, the FOV narrows. A 50mm lens has a 40-degree FOV, 100mm equates to 20 degrees and so on. Most people don’t bother with FOV values, though. It’s easier just to think in focal lengths and get used to what a specific focal length looks like.

The f3.5-5.6 is the maximum aperture that this lens allows. There are two figures in this example because this lens’ maximum aperture varies depending on the focal length. So in this instance, the maximum aperture at 18mm is f/3.5, and at 135mm it’s f/5.6.

The aperture is essentially the size of the hole in the middle of the lens that dictates how much light is let through. A larger aperture means more light, which is particularly helpful when shooting in low light. It means you can use a faster shutter speed to freeze motion or a lower ISO speed to reduce noise.

A larger aperture also gives a narrower depth of field, whereby the subject is in sharp focus but the background and foreground are blurred. A narrow depth of field can flatter portrait shots, and is a major reason why people chose to upgrade from a compact camera or smartphone to an SLR or CSC. Upgrading from a kit lens to a prime can deliver a further big boost to depth-of-field effects.

The depth of field is also influenced by the size of the sensor, the focal length and distance to the subject. For the narrowest depth of field, go for a big sensor, a wide aperture, a long focal length and keep your main subject as near to the lens as possible.

What do the letters IS and USM mean on a camera lens?

Aperture numbers are confusing because lower numbers mean a larger aperture. The way to remember this is to note the ‘/’ in the way they’re written. The aperture is actually the ratio of the size of the hole divided by the focal length, and these are expressed as fractions. So think of f/8 as being 1/8 and f/2 as 1/2 – as 1/2 is a bigger number than 1/8, an f/2 aperture lets in more light than f/8.

The aperture value relates to the diameter of the hole, so an f/2 aperture is twice as big as f/4. The hole is two dimensional, though, which means it’s twice as wide and also twice as tall. That means it lets through four times as much light. To make sense of this, imagine a single square brick. A bigger square that’s made up of two bricks wide by two bricks tall would add up to four bricks. A four-by-four block would need 16 bricks. The same amount of light shines on each brick, so doubling the aperture means four times as much light.

The final bits of this Canon lens’s name are IS and USM. IS is short for image stabilisation, which uses a system of motion sensors and moving lens elements to counteract camera shake when taking photos and videos. This is particularly useful when shooting in low light, or for telephoto photography where camera shake is particularly hard to avoid. Other manufacturers use different acronyms for their stabilisation systems, such as Sony’s OSS, Panasonic’s OIS and Nikon’s VR (for vibration reduction).

USM stands for ultrasonic motor. This is Canon’s upmarket autofocus motor system, which is faster and quieter than other designs. Various other prefixes and suffixes appear on lens model names to denote that they’re premium models or have extra features. A Canon lens with an ‘L’ after the aperture means it’s from its professional range. Panasonic uses the Leica brand on its better lenses, while Fujifilm drops an ‘R’ into its premium model names. You might also see WR to denote that a lens is weather-resistant, or ED for extra-low dispersion, which helps to reduce unwanted optical artefacts.

Ultimately, the mount type, focal length and aperture are the most important specs, stabilisation is quite important and the rest you can research once you’ve found a couple of lenses that fit your requirements.

The difference between buying a lens for a cropped-frame camera vs a full-frame camera

If you own a full-frame camera, focal lengths are relatively easy to understand. However, many SLRs and nearly all CSCs use a sensor that’s smaller than full frame. These are sometimes known as cropped-frame cameras because their smaller sensors are similar to taking a full-frame photo and cropping it.

That means, for a given focal length, the FOV is smaller when it’s mounted on a cropped-sensor camera compared to a full-frame camera. How much smaller is defined by the sensor’s crop factor. Nikon DX SLRs have a 1.5x crop factor, so a 50mm lens behaves like a 75mm lens on a full-frame camera (50 x 1.5 = 75). Micro Four Thirds sensors have a 2x crop, so a 50mm lens is like a 100mm lens on a full-frame camera.

When you buy a compact or bridge camera, the quoted focal lengths are already converted into 35mm-equivalent values. The actual focal length range on a bridge camera might be 4.4-218mm, but because its tiny sensor has a 5.5x crop factor, the lens behaves like a 24-1200mm lens on a full-frame camera. The 24-1200mm spec is the one that’s quoted as it tells you the FOV range for this camera-and-lens combo.

SLR and mirrorless lenses are described using their actual focal lengths, so you’ll need to convert them to 35mm-equivalent values to get a proper understanding of the FOV available. To do this, simply multiply the lens’s focal length(s) by the camera’s crop factor. It’s a bit of a headache, but you only need to do it while buying lenses and not every time you take a photo.

The benefits of buying a prime lens with a fixed focal length

A prime lens has a fixed focal length, so there’s no zoom function. That might sound frustrating if you’re used to a kit zoom lens, but there’s a satisfying discipline to using a fixed focal length, and you don’t have to use the same prime lens all the time.

Omitting the zoom function means designers can concentrate on other things. That usually means a much wider aperture, boosting image quality in low light and giving a shallow depth of field. A popular first lens upgrade is a 50mm prime, often known as a ‘nifty fifty’. A 50mm f/1.8 for Canon, Nikon, Sony and Pentax SLR costs around £120. f/1.8 captures four times more light than f/3.5, and 16 times more than f/5.6.

More upmarket models with an f/1.4 maximum aperture (capturing twice as much light as f/1.8) cost around £400. That’s quite a big price hike for what might be a minimal benefit, but paying more also tends to deliver superior optical performance. That might mean sharper focus, especially at wide apertures, better geometry whereby straight lines in the subject appear perfectly straight, and less evidence of chromatic aberrations, where the green, red and blue elements of the image don’t line up perfectly.

You won’t necessarily want to be shooting at f/1.4 all the time, though. The depth of field can be so narrow that barely any of the subject is in focus – perhaps a person’s left eye but not their right eye. That can work really well in some cases, but most photographers will tend to use apertures around f/2 to f/2.8 for portraits.

The 50mm focal length is known as ‘normal’ because it gives a field of view that’s similar to human vision. That’s somewhat questionable because our vision is actually more of a 180-degree panorama, but the 50mm focal length seems to work pretty well when it comes to capturing the things you can see clearly in front of you. It’s ideal for street photography, still life and product photography, photos of groups of people, full-length portraits, and head and torso shots.

To get the same 50mm equivalent focal length on a cropped-sensor camera you’ll need a shorter prime lens. For cameras with a 1.5x crop factor, go for a 35mm, while for Micro Four Thirds you’ll need a 25mm. You can still use a 50mm, of course, but it will behave like a 75mm on a cropped-sensor SLR.

In fact, that’s not far from 85mm, which is a common focal length for head-and- shoulders portraits. You could capture this type of shot with any lens, of course, simply by moving nearer to or further away from the subject. However, with shorter focal lengths you’d need to get quite close, which can feel intimidating for the subject.

Most manufacturers produce a large number of prime lenses at focal lengths ranging from wide-angle to telephoto, and taking in macro and other specialisms. They tend to offer wider apertures and deliver superior optics compared to their zooming counterparts. Optical stabilisation is unusual in prime lenses but there are exceptions, such as the Panasonic Lumix G 42.5mm f/1.7 ASPH Power OIS and Canon EF 85mm f/1.4L IS USM.

How to buy a wide-angle or fisheye lens for landscape and product photography

Architecture, car and product photographers often use a wide-angle lens to make subjects look dramatic and imposing. Wide-angle works well for landscapes, too, if you want to include a large expanse of foreground in the shot. It’s the standard approach for estate agent photography, where the objective is to make rooms look spacious.

Most kit lenses cover wide angle reasonably well – 18-55mm with a 1.5x crop factor equates to 27-82.5mm on a full-frame camera – but a 24mm or wider equivalent exaggerates the effect. Wide-angle lenses are available as primes or as zooms, with the primes once again tending to offer wider apertures. Wide-angle lenses are a bit more specialised, so prices generally start from around £300. There are exceptions, though, such as the Canon EF-S 10-18mm f4.5-5.6 IS STM (for cropped-sensor Canon SLRs), which costs around £240.

Most wide-angle lenses are what’s known as rectilinear, whereby straight lines in the subject matter appear straight in the photo. The alternative is a fisheye lens, where the view is curved around the centre of the frame. Rectilinear images can look pretty weird at extremely short focal lengths, with a stretched appearance into the corners of frames. For natural rather than man-made subjects, a fisheye lens sometimes looks more natural. It can be a pleasing creative effect in urban environments, too.

How to buy a telephoto lens for sports, wildlife and paparazzi photography

Telephoto simply means a long focal length, typically 150mm and above. These lenses are commonly used for sports, wildlife and paparazzi photography. Less controversially, they’re useful for capturing portraits of people if you want to take natural rather than posed shots. A 200mm (full frame-equivalent) focal length will let you take portraits from the other side of a room.

If you’re photographing a football match or large animals you might use a 70-300mm zoom. For birds or distant animals, a 500mm or bigger focal length will allow the subject to fill the frame. These lenses are expensive, though. That’s why cropped-sensor SLRs are popular for sports and wildlife, as they effectively extend the focal length of lenses. A 70-300mm lens on a cropped-sensor SLR behaves like a 105-450mm lens on a full-frame camera.

There’s a big temptation to go for the longest focal length you can afford, but it’s not the be-all and end-all. If you’re shooting a moving subject such as birds in flight, there’s not much point in a 500mm lens as it will be really tricky to keep the subject in the frame. With today’s huge sensor resolutions, you can always crop a photo and still have enough megapixels for a high-quality image. If you can afford to splash out, it’s worth considering a wider aperture over an extended focal length. A wide aperture will let you use faster shutter speeds to freeze motion without having to increase the ISO speed and put up with the ensuing noise.

Most telephoto lenses will include stabilisation, regardless of whether they’re primes or zooms, because even the smallest of shakes is magnified at longer focal lengths. However, that’s not an issue if you’re using a tripod or if you’re shooting fast-moving subjects such as birds. In this scenario, you’ll need a very fast shutter speed to avoid subject motion blur, and this will also reduce the risk of blur due to camera shake. Therefore you can save a few pounds by doing without stabilisation. For example, Canon sells a 75-300mm f/4-5.6 USM lens for around £260, whereas the stabilised equivalent costs £450. Incidentally, if you want the premium ‘L’ model, it will cost you £1,280.

Tips on buying a versatile lens for travelling and sightseeing

Some lenses take the jack-of-all-trades approach rather than specialising in a specific type of photography. While an 18-55mm lens is fine to get you started, an 18-135mm lens gives a more versatile 7.5x zoom range without the hassle of changing lenses. Canon offers this lens as a premium kit lens option for the EOS 80D, and it’s a worthwhile upgrade for general-purpose photography such as sightseeing. The Tamron 18-270mm f3.5-6.3 Di II VC PZD takes it even further with its 15x zoom range, and is available in Nikon or Canon SLR mounts. The apertures of these lenses are unremarkable and they’re unlikely to excel for image quality compared to lenses with shorter focal length ranges, but there’s a lot to be said for not having to switch lenses when you’re on the move.

There are a few lenses with modest zooms and apertures that compete with primes. Some are frighteningly expensive, such as the Canon EF 24-70mm f2.8L II USM at around £1,700, although the similarly specified Tamron 24-70mm f2.8 Di VC USD SP is £750. For cropped-sensor SLRs, the Canon EF-S 17-55mm f2.8 IS USM may be a better option at £720. Other notable models are the Sigma 18-35mm f/1.8 DC HSM (available for all the big SLR brands) at £650 and the Fujifilm 18-55mm f2.8-4 R LM OIS XF at £620.

A lightweight, slim lens is useful for travelling light. These are known as pancake lenses. There aren’t many to choose from for SLRs but there are quite a few for CSCs. Most are prime lenses and they tend to have relatively unadventurous maximum apertures, but the Panasonic Lumix G 20mm F1.7 II ASPH for Micro Four Thirds cameras (£250) is a notable exception.

The benefits of buying a macro lens or a tilt-shift lens

There are a few other categories of lens that you might like to consider. Macro lenses specialise in photos of small subjects, and they introduce another specification called magnification ratio. A 1:1 ratio means the lens can focus on a subject that’s the same size as the sensor and make it fill the frame. A cropped SLR sensor measures around 25x17mm, so a subject that’s just 25mm wide will stretch from edge to edge of the frame.

The other important specification for macro is the focal length. The longer it is, the further away the camera can be from the subject while still achieving a high magnification. Focal lengths around 100mm are common, with a minimum focus distance of 30cm giving a 1:1 magnification ratio.

A tilt-shift lens does strange things to the geometry of a photo. They’re primarily designed for photographing buildings without the perspective effect that makes parallel lines converge. Imagine you wanted to photograph a tall building with a tilt-shift lens. First, you’d aim the camera directly at the front of the building so the lens is level and square on with the building façade. Then you would adjust the tilt and shift controls on the lens so the composition included the top of the building. The effect is akin to panning around a wide-angle shot rather than tilting the camera. You can achieve a similar effect using Lightroom’s Upright tools, but you’ll get sharper results by doing it with a tilt-shift lens.

Using lenses to create special effects

Macro and tilt-shift lenses can also be used to achieve razor-sharp focus of the foreground, middle distance and background in landscape shots. Alternatively, they can create a narrow strip of sharp focus while blurring the subject at either side. It’s similar to shallow depth-of-field effects from a regular wide-aperture lens, but you can be more prescriptive about what is and isn’t in focus. Tilt-shift lenses aren’t cheap, but they’re a good way to access some unusual creative tricks to help your photos stand out.

A broadly similar but much cheaper alternative is the Lensbaby range. These are sometimes described as toy lenses but with their increasing sophistication that description is no longer entirely accurate.

They’re manual focus only, and rather than attempt to achieve sharp focus throughout the frame, they employ various soft-focus effects. Some allow the focus sweet spot to be moved around the frame so it lines up with the main point of interest. In some cases, it’s possible to achieve similar effects in software, but applying it in-camera helps the effect to be an integral part of the photographic process.

There are various other manual focus lenses available, often with extremely wide apertures, such as the SLR Magic 50mm f/0.95 for Sony E Mount. They can’t compete with the big brands for performance, and the lack of autofocus means you need to take your time, but they’re great for extreme depth-of-field effects and shooting in very low light.

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