Superzoom lenses explained
A key advantage of DSLRs over compact cameras is that you can fit the ideal lens for whatever you're shooting. The downside is that when you're on your travels, you may not want to be weighed down by a big bag full of extra lenses.
With a mighty zoom range, a superzoom lens will typically deliver focal lengths of 18mm at the wide-angle end and anything from 125mm to 270mm at its longest telephoto zoom setting. This gives you an effective zoom range of between 29-200mm and 29-432mm on the Canon APS-C bodies all eight lenses on test are designed for.
The big questions are: how great a zoom range can you get without sacrificing image quality, what features are required to make superzoom lenses really effective, and how much do you need to pay for them?
All-in-one lenses
A standard 18-55mm zoom lens on crop-factor Canons offers respectable wide-angle coverage, equivalent to 29mm, while its effective 88mm focal length at the long end is good for portraiture.
But it runs out of reach if you want to zoom in on distant targets. The general solution is to swap to a telephoto zoom, such as the Canon EF-S 55-250mm, which closes the distance with a maximum effective focal length of 400mm. But sometimes things aren't that simple.
In dusty environments, there's always the risk of your camera ingesting dirt while you're changing lenses, which can end up stuck on the sensor. Nobody likes black blobs on all their shots.
In situations where you need to react quickly to take advantage of unexpected and fleeting photo opportunities, it's also a major disappointment to miss the shot because you were too busy changing lenses.
In these conditions, superzoom lenses reign supreme. They're also ideal as holiday or travel lenses, because they're so compact and lightweight, making them perfect for when you want to carry around the bare minimum of photographic kit.
Back in the days of 35mm film photography, most superzoom lenses tended to offer focal length ranges of around 28-200mm or 28-300mm. For APS-C cameras, 18-125mm and 18-200mm give equivalent zoom ranges. But some lenses, such as the Sigma 18-250mm OS and the Tamron 18-270mm VC, go further still.
Bigger might seem better when it comes to zoom range, but any superzoom lens is a compromise. With added complexity in design and the physics involved in delivering extended zoom ranges, optical performance is likely to be impaired.
Compared with lenses with a modest zoom range, you can expect a superzoom to have less outright sharpness, increased chromatic aberrations and more pronounced distortions.
Optical problems
Distortions can also take on a nonlinear character, so straight lines are not only bowed but can take on a slightly wavy appearance, which is particularly problematic for architectural photography. These degradations in optical quality may be exaggerated in lenses that try to push the boundaries in terms of extreme zoom range.
However, some of the very latest designs manage to maintain good optical quality while giving you the ultimate in zooming versatility.
One thing that all superzoom lenses lack is a 'fast' maximum aperture, and those with the largest zoom ranges typically drop to f/6.3 at the telephoto end. Shooting on a dull day at ISO 100, this can often require shutter speeds of around 1/30 sec, which is far too slow to avoid camera-shake.
Optical image stabilisation is therefore a key feature of good superzoom lenses, and most of the latest designs include a 4-stop stabiliser, enabling you to get consistently sharp handheld telephoto shots at 1/30 sec.
Ultrasonic motor system
Fast, accurate autofocus is a major ingredient for success, especially at longer zoom lengths. Depth of field is greatly reduced at telephoto focal lengths, so focus accuracy becomes critical. Standard micro-motor autofocus systems can be very precise, but are often relatively noisy and can lack speed.
The Sigma 18-125mm f/3.8-5.6 DC OS HSM, the Sigma 18-250mm f/3.5-6.3 DC OS HSM and the Tamron 18-270mm f/3.5-6.3 Di II VC PZD feature quieter Hypersonic or Piezo Drive autofocus - similar to Canon's USM (Ultrasonic Motor) system, which is lacking on both of Canon's superzoom lenses for APS-C cameras.
It's important to realise that not all ultrasonic autofocus systems are created equal. Upmarket 'ring-type' systems are best, because these are virtually silent, very fast and offer the added benefit of full-time manual focus override in One Shot AF mode.
However, the type fitted to the Sigma and Tamron lenses feature a small ultrasonic motor rather than being based on large rings that are mounted around the inner circumference of the lens. They're still quieter and faster than regular micro-motor autofocus systems, but not as near-silent or swift as ring-type ultrasonic systems, and lack full-time manual override. All in all, they're good but not great.
Canon EF-S 18-135mm f/3.5-5.6 IS
Canon EF-S 18-135mm f/3.5-5.6 IS - £350
Despite being a kit lens option for the Canon EOS 7D - arguably the most advanced APS-C camera in the world - the Canon EF-S 18-135mm f/3.5-5.6 IS isn't entirely convincing when it comes to specifications and features. On the surface, it's quite a bare-bones affair, with no focus distance scale or even a zoom lock switch, and the finish feels a bit lacklustre.
Other omissions are any kind of USM (Ultrasonic Motor) autofocus system and - like most of Canon's lenses - it doesn't even come with a lens hood, which costs about £25 extra to buy separately. It's not especially big on zoom range either, with a humble 7.5x zoom (equivalent to 29-216mm).
At least you get Canon's latest 4-stop image stabilisation, which comes complete with auto detection for panning and tripod mounting - although the latter didn't work entirely consistently in our tests.
Image sharpness is merely average, but distortions are reasonably low for a superzoom lens. Chromatic aberrations are quite noticeable but, because it's a genuine Canon lens, you can tune these out in Digital Photo Professional if you shoot in raw quality mode.
18mm sample image from the Canon EF-S 18-135mm f/3.5-5.6 IS
135mm sample image from the Canon EF-S 18-135mm f/3.5-5.6 IS
Canon EF-S 18-200mm f/3.5-5.6 IS
Canon EF-S 18-200mm f/3.5-5.6 IS - £410
Physically, the Canon EF-S 18-200mm f/3.5-5.6 IS is only a single millimetre longer and three millimetres wider than its 18-135mm stable mate, but it's 140g heavier and £60 pricier. It also has a lot more telephoto potential, the long 200mm end being equivalent to a focal length of 320mm on crop-sensor DSLRs.
Build quality feels almost identical in both Canon lenses, although cosmetic differences include a silver-coloured rear edge to the zoom ring. Other similarities include a 4-stop image stabiliser, standard micro-motor autofocus system and the lack of a focus distance scale and lens hood.
As for differences, the 18-200mm has a narrower manual focus ring and features a zoom lock switch.
Sharpness could be a little better throughout the whole zoom range, but distortions are only slightly higher than with the Canon 18-135mm, which is pretty good considering the additional zoom range. Colour fringing proved quite noticeable, but, being a genuine Canon lens, it's fully compatible with in-camera corrections and DPP lens tuning.
The extra telephoto makes this lens a better buy than the cheaper EF-S 18-135mm IS.
18mm sample image from the Canon EF-S 18-200mm f/3.5-5.6 IS
200mm sample image from the Canon EF-S 18-200mm f/3.5-5.6 IS
Sigma 18-125mm f/3.8-5.6 DC OS HSM
Sigma 18-125mm f/3.8-5.6 DC OS HSM - £255
How long do you really need to go? If you're willing to sacrifice a little of the 'super' in your superzoom, and settle for a 7x zoom range equivalent to 29-200mm, this Sigma lens has a lot going for it. Quite compact but with a reassuring heft, the 18-125mm feels particularly solid and well built. The zoom and focus rings have a smooth feel to them and - more remarkably for a superzoom lens - the Sigma doesn't suffer at all from zoom creep.
The HSM (Hypersonic Motor) autofocus proved only marginally quieter and faster than the standard micro-motor systems in the Canon lenses, but was very accurate even in very tricky conditions.
Like the larger Sigma 18-250mm on test, this lens also features Sigma's latest-generation 4-stop OS (Optical Stabilizer), which performed every bit as well as the Canon and Tamron equivalents.
Along with its impressive build quality and advanced features, optical quality is very good. Sharpness and contrast proved slightly better than with the Canon lenses, especially at large apertures. Distortions are well controlled, which is an upside of the more modest zoom range. It's a great buy for the price.
18mm sample image from the Sigma 18-125mm f/3.8-5.6 DC OS HSM
125mm sample image from the Sigma 18-125mm f/3.8-5.6 DC OS HSM
Sigma 18-200mm f/3.5-6.3 DC
Sigma 18-200mm f/3.5-6.3 DC - £175
Unfeasibly small for a superzoom lens, this Sigma is barely larger than the Canon EF-S 18-55mm IS kit lens supplied with the Canon EOS 1100D and 600D. Yet it delivers an impressive 11.1x zoom range, equivalent to 29-320mm. As well as being relatively tiny, it's just two-thirds the weight of Canon's 18-200mm lens, making it a tempting travel companion.
Look a little deeper and the Sigma is less impressive. The downsized build is partly due to the lack of optical stabilisation and, coupled with a meagre maximum aperture of f/6.3 at the telephoto end, sharp handheld telephoto shots are a major challenge in anything other than bright, sunny conditions.
The lens also lacks Sigma's HSM autofocus system, and the standard micro-motor fitted proved much slower and rather noisier than those fitted to the Canon lenses. In dull lighting conditions there was also more hunting than usual involved, as the AF system struggled to lock on to targets.
Sharpness proved only average, and colour fringing was very noticeable towards the corners of the frame. It's less than half the price of some lenses in the group, but still relatively poor value.
18mm sample image from the Sigma 18-200mm f/3.5-6.3 DC
200mm sample image from the Sigma 18-200mm f/3.5-6.3 DC
Sigma 18-200mm f/3.5-6.3 DC OS
Sigma 18-200mm f/3.5-6.3 DC OS - £295
This newer edition of Sigma's 18-200mm lens is much bigger and 205g heavier than its older sibling, and has a larger filter size of 72mm, as opposed to just 62mm. The biggest difference, however, is that this lens features an all-important Optical Stabilizer. Handheld shooting is therefore much easier at telephoto zoom settings, given the slow maximum aperture of f/6.3.
It's not all good news, however, because despite being the 'new' version, this lens is still over four years old, and was actually one of the very first Sigma lenses to feature a stabiliser. As such, it's the company's first-generation system, which only delivers a 3-stop advantage, whereas all the other stabilised lenses in our test group give a 4-stop benefit.
Build quality feels pretty solid, and the layout is very similar to the smaller and lighter Sigma 18-125mm f/3.8-5.6 DC OS HSM. Optical quality is good rather than great, very similar to the Canon 18-200mm.
There's no HSM autofocus and AF performance is quite slow, noisy and prone to hunting. Overall, it's better than the original Sigma 18-200mm, but not as good as the other two Sigma lenses in the group.
18mm sample image from the Sigma 18-200mm f/3.5-6.3 DC OS
200mm sample image from the Sigma 18-200mm f/3.5-6.3 DC
Sigma 18-250mm f/3.5-6.3 DC OS HSM
Sigma 18-250mm f/3.5-6.3 DC OS HSM - £400
The newest and mightiest of Sigma's superzoom lenses, the 18-250mm is pretty much the same size and weight as the company's older 18-200mm OS lens and has the same 72mm filter size, yet offers three key advantages.
First of all, the effective telephoto reach extends to 400mm instead of 320mm. Secondly, that reach is made all the more usable in handheld shooting thanks to the inclusion of Sigma's latest generation 4-stop image stabiliser, which works a treat.
Finally, the lens comes complete with HSM autofocus, which we found to be much quieter and a fair bit quicker than with either of Sigma's 18-200mm lenses. Even so, autofocus is only a bit quieter and not much faster than with the Canon superzooms. Overall build quality is very good and, for a relatively heavy lens, zoom creep is minimal.
The lens proved sharper than the Canon lenses, especially at wide aperture settings. Distortions were less pronounced as well, compared with the Canon 18-200mm and Sigma 18-200mm lenses. For power and versatility, this is the best Sigma lens in the group and a better buy than either of the Canon lenses.
18mm sample image from the Sigma 18-250mm f/3.5-6.3 DC OS HSM
250mm sample image from the Sigma 18-250mm f/3.5-6.3 DC OS HSM
Tamron 18-200mm f/3.5-6.3 XR Di II Macro
Tamron 18-200mm f/3.5-6.3 XR Di II Macro - £170
A throwback to the days of non-stabilised superzoom lenses, the Tamron 18-200mm f/3.5-6.3 XR Di II Macro was one of the first superzooms to be designed exclusively for APS-C cameras, and was launched back in 2005. The build is only slightly larger than Sigma's extremely compact non-stabilised 18-200mm, and it's marginally lighter, at just 398g.
Build quality feels quite good and, like the Sigma 18-125mm f/3.8-5.6 DC OS HSM, there's no hint of zoom creep. In other areas, the Tamron lens is quite disappointing. Autofocus is quite shrill and noisy, along with a slow action that's also prone to AF hunting, where the system oscillates back and forth before locking on to its target.
Like the original Sigma 18-200mm, the lack of stabilisation coupled with a slow maximum aperture of f/6.3 at the telephoto end makes handheld shooting quite a hit-and-miss affair.
The Tamron's sharpness wasn't quite as good as other lenses on test, even when reducing the aperture to f/8. Despite having a 'Macro' badge, the maximum magnification factor of 0.27x is only about the same as most other lenses in the group, and is actually slightly less than with the Tamron 18-270mm f/3.5-6.3 Di II VC PZD.
18mm sample image from the Tamron 18-200mm f/3.5-6.3 XR Di II Macro
200mm sample image from the Tamron 18-200mm f/3.5-6.3 XR Di II Macro
Tamron 18-270mm f/3.5-6.3 Di II VC PZD
Tamron 18-270mm f/3.5-6.3 Di II VC PZD - £495
When we've previously used the Tamron 18-270mm VC, we liked it a lot, but had two reservations: the standard micro-motor autofocus system was noisy and the zoom ring felt jerky. Both of those issues have been resolved with the introduction of a PZD (Piezo Drive) autofocus motor and a smoother-acting zoom ring.
However, the new Tamron 18-270mm f/3.5-6.3 Di II VC PZD definitely isn't just the old model with a new AF system – it's a completely new lens. The 4-stop VC (Vibration Correction) system is significantly smaller, yet proved equally excellent in our tests.
The optics are also redesigned, the result being that the lens is much smaller and lighter than the old model, or the Sigma 18-250mm OS. Even the filter thread has shrunk, from 72mm to 62mm.
Contrast proved very impressive, and sharpness was well maintained into the corners of the frame. Colour fringing was minimal at the centre of the image, but quite noticeable towards the corners. The class-leading 15x zoom range is great to have, but comes with a fair bit of barrel distortion at the widest-angle zoom setting.
18mm sample image from the Tamron 18-270mm f/3.5-6.3 Di II VC PZD
270mm sample image from the Tamron 18-270mm f/3.5-6.3 Di II VC PZD
Superzooms for full-frame Canon cameras
The once large collection of superzoom lenses available for full-frame Canon DSLRs has been whittled down to just two.
By far the less expensive is the Tamron 28-300mm f/3.5-5.6 XR Di VC, which sells for about £500. It's remarkably compact and lightweight for a full-frame superzoom, measuring 78 x 99mm and weighing 555g. The overall performance of this lens is impressive, and it's now the only choice for budget-conscious full-frame shooters.
For those with big pockets – or at least fat wallets – the money-no-object option is the Canon EF-S 28-300mm f/3.5-5.6L IS USM, which sells for around £2,100. L-series hi-tech trimmings include faster apertures, rugged build quality, and a posh white paint job.
You also get advanced ring-type USM autofocus and 3-stop image stabilisation. It's a big, heavy beast, however, measuring 92x184mm and tipping the scales at 1.67kg.
While being designed for full-fame cameras, both of these lenses are compatible with Canon DSLRs that have smaller image sensors. However, you'll lose out at the wide-angle end but get a more generous telephoto reach, with an effective zoom range of 45-480mm.
Verdict: best superzoom for Canons
Non-stabilised superzoom lenses have really had their day. The combination of long telephoto focal lengths and fairly small maximum apertures of around f/6.3 runs the ever-present risk of camera-shake.
So while the ageing non-IS version of the Sigma 18-200mm and Tamron 18-200mm are quite cheap, they're not the best value.
On a tight budget, we'd forego extra telephoto reach and buy the Sigma 18-125mm DC OS HSM, which offers impressive optical quality and comes with 4-stop stabilisation and Hypersonic autofocus.
Both Canon lenses are good rather than great, with basic feature sets, considering their fairly high prices. Image quality is only average, but at least you get the advantage of in-camera corrections for peripheral illumination on most of Canon's latest cameras, plus the option of lens tuning in Digital Photo Professional.
The biggest hitters in the group are the Sigma 18-250mm DC OS HSM and the new, radically redesigned, Tamron 18-270mm Di II VC PZD.
For compactness, light weight, impressive image quality and class-leading 15x zoom range, the Tamron wins out.
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