Best zoom lens upgrades explained
Standard zoom lenses are the ones that most of us use for the vast majority of our shooting. The zoom range of around 18-55mm translates to a focal length of about 28-80mm on a typical DSLR, thanks to the crop factor of an APS-C sized sensor.
This provides a generous field of view at the wide-angle end, stretching to decent short telephoto reach at the long end, ideal for portraiture or for getting that little bit closer to objects in the middle distance to help us get a perfect shot.
Considering that a standard zoom is such an everyday lens, it pays to use a good one. And you can't help thinking that the kit lenses supplied with most cameras are built down to a price.
Without wanting to pick on anybody in particular, let's take the Canon EF-S 18-55mm f/3.5-5.6 IS as an example, which is supplied as a kit lens with the Canon EOS 550D. The Canon EOS 600D has the new II version, which is supposed to be optically the same.
Considering the wealth of features and technical prowess of these cameras, the kit lens looks like a bit of a mismatch. It also feels cheap and plasticky, right down to the mounting plate, which is made of plastic rather than metal. Furthermore, it lacks Canon's refined USM (UltraSonic Motor) autofocus system, and the front element rotates while focusing, which makes rotation- specific filters such as polarisers and ND grads a pain to use.
At the other end of the scale, pro-level standard zoom lenses such as the Nikon AF-S DX 17-55mm f/2.8G IF-ED can be expensive at over £1,000. These lenses are often big and heavy as well, making them feel a bit unbalanced on relatively lightweight bodies. Thankfully, there are plenty of options that bridge the gap between cheap kit lenses and professional exotica to choose from.
Constant aperture
One of the features that's usually taken for granted on professional standard zoom lenses is that they're 'constant aperture' lenses. You can expect a fast maximum aperture, typically f/2.8, which is available all the way through the zoom range.
When you're shooting with studio lighting or in manual exposure mode, it's a real bonus to know that your maximum available aperture won't decrease from, say, f/3.5 to f/5.6 as you zoom towards the telephoto end.
The Sigma 17-50mm f/2.8 EX DC OS HSM, Tamron SP AF 17-50mm f/2.8 XR Di II VC LD Aspherical and Tokina AT-X 16-28mm f/2.8 PRO FX lenses all have a constant maximum aperture of f/2.8, while the Pentax smc DA 16-45mm f/4.0 ED AL has a constant maximum aperture of f/4. The downside is that the zoom range itself is relatively modest at between 1.75x and 2.9x.
By contrast, the Canon EF-S 17-85mm f/4-5.6 IS USM, Nikon AF-S DX 16-85mm f/3.5-5.6G ED VR, Olympus Zuiko Digital 14-54mm f/2.8-3.5 II and Sony DT 16-80mm f/3.5-4.5 ZA Vario-sonnar T* have a greater zoom range of between 3.9x and 5.3x, but the maximum aperture shrinks by about a stop as you zoom from wide-angle to the telephoto end.
Another bonus of having a fast f/2.8 lens is that many cameras can take advantage of the increased light transmission to enable more decisive autofocus in dull conditions. This is because the central AF point often has a higher sensitivity rating, which boosts performance when coupled with lenses that are f/2.8 or faster.
Autofocus itself is often faster and quieter than with basic kit lenses. The system fitted to the Canon lens in the group is based on the upmarket 'ring-type' ultrasonic motor, which comes with full-time manual override for preferred adjustments, unlike Canon's more basic micro-motor or standard USM systems.
This is great for tweaking the focus setting after autofocus has been achieved without having to switch between autofocus and manual focus modes which can cost you precious time. The AF-S (Silent Wave) system fitted to the Nikon lens on test offers the same range of trickery. Sigma's HSM (HyperSonic Motor) on its 17-50mm lens is also quiet, but it lacks the full-time manual override featured on some of Sigma's HSM lenses.
Zoom lens compatibility and key features
All but two of the zoom lenses we tested are designed for APS-C sensors - the Olympus Zuiko Digital 14-54mm f/2.8-3.5 II is designed for the smaller Four Thirds sensor, and the Tokina AT-X 16-28mm f/2.8 PRO FX for full-frame. Key advantages are that these lenses tend to be smaller, lighter in weight and cheaper to manufacture, which makes them easy to handle and less expensive to buy.
Given the massive dominance of APS-C compared with full-frame sensors in the DSLR market, it's strange that Tokina has discontinued its 'DX' format constant-aperture 16-50mm lens. Instead, the company has just launched an 'FX' full-frame 16-28mm f/2.8 lens, which is equally compatible with full-frame and APS-C Canon and Nikon bodies.
While the Tokina optic is typical of wide-angle, full-frame zoom lenses, there are nevertheless advantages to using this type of lens on an APS-C body. Vignetting (darkened corners of the image frame) should be much less noticeable, especially at large apertures, and sharpness may be better at the extreme edges and corners of the frame. This is because the larger image circle produced by the lens is cropped so that you're only using the central area, where the quality is at its best.
The downside of wide-angle full-frame lenses are usually increased bulk and weight - making them harder to handle - they're more expensive, they lack zoom range and they generally don't have optical stabilisation.
Zoom lens features to look for
Zoom range
Differences in zoom range are exaggerated once you take APS-C crop factors into account. The effective range of a 16-85mm lens compared with an 18-55mm is about 24-128mm as opposed to 27-83mm.
Distance scale
Often lacking on cheap kit lenses, a focus distance scale is incredibly useful for setting hyperfocal distance for maximising depth of field, as well as for setting up manual flash power output.
Autofocus system
Fast, quiet autofocus is massively useful. Top performers include Canon USM (UltraSonic Motor), Nikon AF-S (AutoFocus Silent Wave) and Sigma HSM (HyperSonic Motor) systems.
Front element
Front elements that don't rotate during focusing make life much easier when using rotation-specific filters such as circular polarisers, and enable the use of optimised, petal-shaped lens hoods.
Constant aperture
A large, constant aperture enables fast shutter speeds and tight depths of field when shooting. If you set a large aperture, it will remain fixed throughout the entire zoom range.
Optical stabilisation
One of the most useful innovations in lens design, optical image stabilisation enables consistently sharp handheld shots in the absence of in-camera, sensor-shift stabilisation.
Canon EF-S 17-85mm f/4-5.6 IS USM
The first step up Canon's ladder of standard zoom lenses, at least from the kit lens supplied with the 550D and 600D, is the EF-S 17-85mm. It's better built, with a much sturdier feel than the Canon EF-S 18-55mm f/3.5-5.6 IS kit lens for those cameras.
Street price : around £350
Read the full Canon EF-S 17-85mm f/4-5.6 IS USM review
Image tests
Sharpness Test
Centre frame sharpness is good throughout the focal range of the lens, but the edge sharpness at 17mm is soft.
Fringing test
While there's little sign of fringing at the centre of the frame, towards the middle and edge, there's a slight visible blue and red influence.
Distortion test
At the widest focal length distortion is very apparent. At 24mm distortion is minimal, increasing to a mild pinch at 85mm.
Image test verdict
Performance from the Canon lens is average. Its good performance is marred by soft edges and visible fringing at the widest focal length.
Score: 3/5
Nikon AF-S DX 16-85mm f/3.5-5.6G ED VR
With an effective zoom range of 24-127.5mm on Nikon APS-C cameras, this lens is generous at both the wide-angle and telephoto ends of the scale. Despite this, it's surprisingly compact and sturdily built. Extras include a petal-shaped lens hood and soft pouch.
Street price : around £400
Read the full Nikon AF-S DX 16-85mm f/3.5-5.6G ED VR review
Image tests
Sharpness Test
Sharpness is average, with results for centre to middle frame sharpness consistent throughout the focal range.
Fringing test
At all focal lengths and across the frame the Nikon lens produces little sign of fringing, with mild signs of blue at the widest focal length.
Distortion test
At 16mm there are visible signs of distortion. As the focal length is increased it disappears, before a slight pinch from 35-85mm.
Image test verdict
Centre sharpness proves consistent throughout the focal range. Fringing at all focal lengths is minimal, but distortion is apparent at 16mm.
Score: 3/5
Olympus Zuiko Digital 14-54mm f/2.8-3.5 II
Designed specifically for the Four Thirds SLR system, the Olympus 14-54mm has a useful effective zoom range of 28-108mm.
Street price : around £580
Read the full Olympus Zuiko Digital 14-54mm f/2.8-3.5 II review
Image tests
Sharpness Test
Images from the Olympus lens are visibly softer than the others in the group test, and it's especially noticeable when it's at 54mm.
Fringing test
At 14mm, red fringing is visible at the very edges of the frame, but as the focal length increases the influence drops off.
Distortion test
Distortion performance is good, with mild barrelling at 14mm. The 2x crop factor of the Four Thirds sensor means wide angles are required.
Image test verdict
Throughout the focal range sharpness is low, but there's only a little softening towards the edges. Fringing and distortion results are good.
Score: 3/5
Pentax smc DA 16-45mm f/4.0 ED AL
Noticeably larger and about one-and a-half times heavier than the SMC Pentax DA 18-55mm f3.5-5.6 AL WR kit lens, the 16-45mm gives you better wide-angle coverage. The flip side is that you lose telephoto reach, with a maximum effective focal length of 67.5mm.
Street price : around £235
Read the full Pentax smc DA 16-45mm f/4.0 ED AL review
Image tests
Sharpness Test
The Pentax lens shows good sharpness at all focal lengths. At 35mm, however, there's a slight softening towards the edges.
Fringing test
Fringing at the centre frame is minimal, but there's a blue trace at all focal lengths towards the middle and edge frame.
Distortion test
Barrel distortion is apparent at 16mm and 20mm. However, at longer focal lengths distortion is minimal.
Image test verdict
The Pentax performs well, delivering good and consistent sharpness and distortion results. Fringing is visible near the edges of the frame.
Score: 4/5
Sigma 17-50mm f/2.8 EX DC OS HSM
It's not often that an independently manufactured lens costs more than some camera manufacturers' own-brand rivals, but this Sigma is a bit special. Unlike the Canon and Nikon lenses on test, the Sigma 17-50mm boasts a fast, constant aperture of f/2.8 that remains fixed throughout the zoom range.
Street price : around £575
Read the full Sigma 17-50mm f/2.8 EX DC OS HSM review
Image tests
Sharpness Test
At all focal lengths, the Sigma optic shows good sharpness at the centre and middle frame, but there's a slight softening towards the edges.
Fringing test
At all focal lengths, there's a little sign of fringing at the centre frame, but towards the edges there's a mild influence of blue and red.
Distortion test
At 17mm and 21mm there's slight barrel distortion, and above this, pinch distortion is only minimal and barely visible.
Image test verdict
Sharpness at all focal lengths, and especially at the centre of the frame, is very good. Fringing and distortion are also minimal.
Score: 4/5
Sony DT 16-80mm f/3.5-4.5 ZA Vario-sonnar T*
From the legendary Carl Zeiss stable of Vario-Sonnar lenses, the DT 16-80mm is a class act that delivers a powerful 5x zoom range, equivalent to 24-120mm. The bland styling isn't much to look at, but the zoom and focus rings work smoothly.
Street price : around £630
Read the full Sony DT 16-80mm f/3.5-4.5 ZA Vario-sonnar T* review
Image tests
Sharpness Test
Centre sharpness at all focal lengths is good, but it starts to drop towards the middle frame and plummets towards the edge.
Fringing test
There's little sign of fringing at the centre, but towards the edge at 16mm, 24mm and 80mm there's a green influence.
Distortion test
Barrel distortion is apparent at 16mm, but from 24mm through the rest of the focal range, distortion is only minimal.
Image test verdict
Centre-to-edge sharpness is good, but drops dramatically towards the edges. Fringing at the two focal extremes is apparent towards the edges.
Score: 3/5
Tamron SP AF 17-50mm f/2.8 XR Di II VC LD
Most of the alphabet seems to feature at some point in the Tamron's full title, but these abbreviations promise plenty of features. SP signifies Super-Performance, based on three XR (Extra-Refractive) elements, an LD (Low-Dispersion) element and two Aspherical elements in its construction.
Street price : around £345
Read the full Tamron SP AF 17-50mm f/2.8 XR Di II VC LD Aspherical review
Image tests
Sharpness Test
Centre sharpness is good at all focal lengths, but edge sharpness drops dramatically at the widest focal length.
Fringing test
At 17mm towards the edge of the frame there's a mild sign of red and blue fringing. At all other focal lengths the influence isn't visible.
Distortion test
Barrel distortion is visible at 17mm and 24mm. Distortion is heavy at the widest focal length, but is good throughout the rest of the range.
Image test verdict
The Tamron lens shows good centre sharpness throughout the focal range. However, fringing and distortion is visible at 17mm.
Score: 4/5
Tokina AT-X 16-28mm f/2.8 PRO FX
Much bigger than most lenses, and at more than twice the weight of some, the Tokina AT-X 16-28mm f/2.8 PRO FX is a chunky lens. That's because while other lenses are designed solely for use on cameras with APS-C or Four Thirds sensors, the Tokina is fully compatible with full-frame cameras.
Street price : around £895
Read the full Tokina AT-X 16-28mm f/2.8 PRO FX review
Image tests
Sharpness Test
Centre sharpness at all focal lengths is about average. However, sharpness drops towards the middle to edge frame.
Fringing test
The Tokina shows little visual signs of fringing at any focal length. There's a slight blue fringe towards the edge of the frame, however.
Distortion test
There's slight barrel distortion at 16mm, but the effect is minimal. Throughout the rest of the focal range there's little distortion.
Image test verdict
Overall sharpness for the Tokina lens is average, and while there's a drop towards the edges it isn't as dramatic as the others in the test.
Score: 3/5
Zoom lens benchmarks
All of the lenses on test have a similar widest focal length, but the results show a difference in performance throughout their focal ranges.
The Canon and Nikon lenses show similar characteristics, but both suffer from visible barrel distortion at their widest focal lengths.
The Sony and Tamron optics have excellent centre and middle frame sharpness, but at 16mm and 24mm this softens towards the edge, and distortion is apparent at the widest focal lengths, with signs of fringing.
The Tokina lens produces average results for sharpness, but results for fringing and distortion are good. The Olympus lens produced the lowest sharpness results, with visible softness and fringing at the widest focal length.
At the top of the group are the Sigma 18-50mm and Pentax 16-45mm. Both show excellent sharpness at all focal lengths and only some slight distortion. The blue edge fringing of the Pentax means that the Sigma just beats it.
Verdict: best zoom lens upgrade
With its fast, constant aperture of f/2.8, the Sigma 17-50mm provides great control over depth of field. Image quality is impressively sharp and crisp, even at the widest aperture. This is true throughout the entire zoom range. Build quality feels solid and robust, and little luxuries include fast, near-silent HSM (HyperSonic Motor) autofocus and a four-stop optical image stabiliser.
It's one of the more expensive lenses here, but it's worth every penny, and is our favourite.
The Tamron 17-50mm is also a strong contender, again offering a constant maximum aperture of f/2.8 throughout the zoom range and boasting four-stop vibration correction. Autofocus is a little noisy and sluggish, but then again, the Tamron lens is £230 cheaper than the Sigma optic.
Our only reservation is that a previous sample of this lens we tested last year wasn't nearly as sharp as the one Tamron sent us this time around, which puts a question mark over the manufacturer's quality control.
We had the opposite experience with the Nikon 16-85mm - our review sample lacked the razor sharpness that we've experienced with previous samples. Based on past samples, we've awarded this lens the best for Nikon badge, but it's a close call against the Sigma.
At least Canon's 17-85mm proved entirely consistent - this lens has suffered dreadful chromatic aberration in past lens tests, and this time was no exception. Apart from that, it's a good lens for the price, if you're willing to tune out the colour fringing at the editing stage. The Pentax 16-45mm has similar issues, but automatic in-camera correction is available in current Pentax SLRs, making the lens great value for money.
Best for Canon APS-C format users:
Tamron SP AF 17-50MM f/2.8 XR Di ii VC LD Aspherical
What's good: fast f/2.8 constant-aperture and good sharpness.
What's bad: no full-time manual override.
Our verdict: outperforms similarly priced lenses, but quality control could be an issue.
Best for Pentax users:
SMC Pentax DA 16-45MM f4.0 ED AL
What's good: sharpness is good.
What's bad: Wide-angle distortion, and noticeable chromatic aberration.
Our verdict: Automatic in-camera lens correction makes this a bargain.
Best for Nikon DX format users:
Nikon AF-S DX 16-85MM f/3.5-5.6G ED VR
What's good: excellent 5.3x zoom range, great handling, four-stop vibration reduction
What's bad: we have had samples that are inconsistent for sharpness
Our verdict: if you can live without a fast, constant aperture, this lens is great.
Best for Olympus Four Thirds users:
Olympus Zuiko Digital 14-54MM f2.8-3.5 ii
What's good: Dust and moisture seals, high-precision manual focus ring.
What's bad: image quality was below average.
Our verdict: expensive, but the choice is limited in four thirds fit.
Best for Sony APS-C format users:
Sigma 17-50mm f/2.8 EX DC OS HSM
What's good: fast f/2.8 constant-aperture.
What's bad: colour fringing can be slightly noticeable towards the edges of the frame.
Our verdict: An excellent lens, and cheaper than the sony lens we tested.
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