Users of Pentax film and digital cameras can use this lens, with its full image circle covering both APS-C sensirs and the 35mm frame. The lens is digitally optimised with SMC coatings to reduce flare, reflections, ultraviolet rays, thereby improving contrast.

The barrel construction is of a high quality while the internal optics are arranged as eight elements in seven groups. A nice touch is the focus ring which allows direct switching from AF to manual just by focusing, which would normally damage the motor on a lesser lens. A focus clamp is also conveniently situated on the barrel to lock focus in position, which I found very useful.

Pentax still incorporates a good old-fashioned aperture ring on the lens. Users of *ist series cameras need to lock this in the A- position as aperture is controlled on the camera body, but it’s nice to see that Pentax still offers backwards compatibility for more manual film cameras.

If I was purely after image quality and used a Pentax, then this lens is the one I would use over the 100mm, with higher sharpness throughout the aperture range, if only marginally. The Pentax 50mm shows consistent control of fringing with some chromatic aberration, but it’s only just visible.