As part of my search for a short telephoto prime lens, I rented the Sigma 105 DG Macro lens in the Pentax mount and walked around False Creek, Granville Island and a bit of Commercial Drive to test the lens as a short telephoto (not a macro lens).
This lens did not feel as well-built as the 77mm FA lens, but seemed to respond well to the AF control of the K5 camera. I did not have time to test all of the F stops to see how the sharpness varied but like most lenses it seemed sharper two stops closed down from its widest aperture. The purple fringing at F2.8 was minor and hardly noticeable.
The following are some pictures of buildings that have slight PF when the 100% crop is viewed.
100% view of the top section of the building:
The next set of pictures were taken at F4 and demonstrate the bokeh of the lens. All photos are handheld.
While this lens was OK, I really did not get too excited by any of the pictures that I took. I was much more impressed with the FA77mm lens despite the PF at the wide open apertures. I decided to purchase the FA77mm lens and will post more pictures using this lens in the near future. I will use this plus the DA35mm and the A24mm lens instead of my wide-angle zoom, to help bring more artistic qualities into my photos using the shorter depths of field that is possible with these prime lenses.