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