Olympus Zuiko Digital ED 9-18mm f/4-5.6 - £490
Very compact and lightweight, the Olympus 9-18mm lens is only half the weight of the Sigma 8-16mm lens and is a whole inch shorter. The main reason for this is that it's scaled down for the Four Thirds system, which has a rather smaller sensor than APS-C cameras.
Although it saves on size and weight, the 2.0x crop factor works against you for wide-angle shooting. This 9-18mm lens only has an effective zoom range of 18-36mm on Olympus DSLRs, so the field of view is narrower than with, for example, a Nikon DSLR and a 10-24mm lens.
Autofocus is fairly quiet if not particularly fast, and it tended to hunt a bit in some of our tests. The manual focus ring has an electronic rather than mechanical coupling, with manual override available through camera menu options. The only real drawback of the focusing system is that a focus distance scale isn't available.
Unlike previous review samples of this lens we've seen, sharpness impressed throughout the zoom range, at least at f/8 and narrower apertures. In fact, it rules the roost at f/16, but is more consistent across its focal length range at f/8, where it comes second for sharpness. But it was a different story shooting at the widest apertures, with a distinct lack of detail, especially at the widest end of the zoom range. Performance was good in terms of distortion, chromatic aberration and vignetting. Based on this sample, the 9-18mm optic is a good buy.
Resolution sharpness test
At all focal lengths centre sharpness is excellent. Although it drops off towards the edges at all focal lengths, the lens resolves detail well.
At 9mm there are slight signs of green and red fringing towards the edge. At 14mm and 18mm the fringing increases.
At 9mm and 14mm there are signs of barrel distortion, but both values are low. At 18mm distortion is almost zero.
Image test verdict
Sharpness and fringing at all focal lengths and across the frame is good, although there is some drop off in quality towards the edges.