Pentax smc D-FA 100mm f/2.8 Macro WR - £480
Wide-open performance isn't too good, and the improvements between f/8 to f/16 are confined to the centre of the lens.
There's fringing at the centre, and it gets considerably worse towards the edges, but recent Pentax SLRs can correct lateral chromatic aberration.
Distortion control is excellent, with just minimal warping. Were it not for the superior Sigma lens, the Pentax would just edge its way to the top.
Image test verdict
It's a shame that wide-open sharpness and control over chromatic aberration are poor, because otherwise this is a fine, solid lens.