Pentax smc DA 18-135mm f/3.5-5.6 ED AL [IF] DC WR - £530
relative newcomer to the superzoom market, the Pentax 18-135mm is the smallest and lightest in the group. Naturally, downsizing is helped by the fact that it has a modest zoom range. Even so, the effective focal range of 27-202mm gives plenty of versatility when shooting.
In our tests, the Pentax optic was a joy to use with its oversized, silky-smooth zoom ring. It suffered no zoom creep, which is just as well because the lens doesn't feature a zoom lock. The built-in autofocus motor is extremely quiet, and comes complete with full-time manual override – Pentax calls it a 'Quick-Shift' focus system. Our only reservation is that a larger focus ring would be easier to use.
Considering the lens's relatively modest zoom range, we'd expect less compromise in terms of the optical quality. Sure enough, centre sharpness is exemplary throughout the entire zoom range, but sharpness drops off disappointingly at the edges of the frame, especially at longer focal lengths.
Colour fringing towards the corners of the frame is among the worst of any lens on test, and distortion is also poor, especially at the longer end of the zoom range. On the plus side, all current Pentax DSLR bodies have built-in automatic correction for colour fringing and distortion. Even so, we'd expect better optical quality considering the relatively short zoom range and the high price.
Centre sharpness at all focal lengths is excellent. However, as with other lenses in the test, the sharpness drops towards the edges.
Fringing at the centre is low at all focal lengths, but at the widest end of the range there are signs of blue fringing, and at the longest, green.
Distortion at the widest focal length is average, and easily correctable at the middle and longest. Pinch distortion is higher than average.
Image test verdict
The Pentax resolves good centre sharpness across the focal range. Fringing at the extremes of the focal range is noticeable at the edges.