I have both the Takumar-F version of this lens, which I got first and seems to be more readily available in Japan, and the SMC version. I didnít realise there were two versions at first. I liked the Takumar-F version, so when I found out that there was a supposedly superior SMC version, I got that too. I havenít been able to detect any real-world differences between the two lenses, even when testing them side by side. The reflections on the surface of the front element look different, so I donít doubt there is a difference in the coating, but it just doesnít seem to affect image quality much. This picture shows the differences in markings between the two lenses (Takumar-F on the left, SMC Pentax on the right).
Iíve used this with a K20D and a K-01, and all comments relate to my experiences on APS-C cameras.
Itís a very interesting lens. The zoom range may seem to be limiting, but it's actually very good for pictures of people at outdoor events. I often carry this lens in a very compact kit with a K-01 and a DA21 for any wide-angle shots. It also has a macro function, so it's pretty versatile overall.
It's remarkably small and unobtrusive, no bulkier than a prime, but itís fairly weighty (more than a 18-55 kit lens). The 49mm thread means that it can share filters with the DA limiteds lenses, but note that the front element rotates, so C-PL filters are a pain. The surface plastic feels cheap to the touch, especially the focus ring, but I think itís pretty solidly made inside. It focuses very quickly and accurately, but itís the noisiest lens Iíve tried in operation.
In terms of image quality, it's surprisingly sharp stopped down a little. Bokeh is usually nice enough and you can get some decent separation between subject and background at 70mm for portraits. Thereís a bit of CA, but Iíve seen worse on FA lenses. Flare can affect shots quite badly. I find the screw-on hood for the DA40 works very well with this lens.
It's great to see you back on the forum! Have you considered joining the community?