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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