Originally posted by Rick Woodward
I am looking for a decent (but not incredibly expensive) long lens for my Pentax K10D.
Ideally I'd like to go to 500mm, but could easily settle for 400mm as the longest focal length.
It doesn't have to be a zoom - but I am open to that.
Weight is a factor - I want to use this lens hand held or at least on a mono-pod at airshows.
I am completely confused by Sigma and Tamron offerings and not convinced that many have Pentax fitting mounts.
What do people recommend? Please tell me your experiences - good and bad!
Thanks.
Rick Woodward
There is currently no 400mm lens in Pentax's catalog, so there is strong demand for 400mm lenses among Pentax users. Most independent makers have discontinued their 400mm primes, so zooms are the only alternatives left for Pentax users looking for a new lens. The Sigma 50-500mm and Tamron 200-500mm lenses get very good reviews but are quite expensive. The Sigma 135-400mm is also good, somewhat better than the Tokina AT-X 80-400mm, but not as good as the Sigma and Tamron 500mm offerings. For used lenses, the Sigma APO Macro 400mm is the sharpest prime, followed by the Tokina AT-X 400mm, the Sigma APO 400mm, and the Tokina SD 400mm manual focus and finally the Sigma non-APO 400mm in the order of decreasing sharpness.
500mm mirror lenses are available. The Tamron is probably the best among them, although Tokina and Sigma also have good ones. The Sigma is a 600mm. Problem with mirrors is their awful bokeh, and the very shallow depth of field, which makes accurate focusing very important. They are also slower. Because part of the front lens is blocked by the mirror housing, the actual apertures of these lenses is closer to f9-9.5, not f8 as marked on the lens.
The Sigma 100-300mm f4 also gets very good reviews, and it is pretty sharp at 300mm, which is quite rare for a zoom. Adding a 1.4x, 1.7x or 2x teleconverter to it may be a good solution. Bad thing is that all of these options are more expensive in Pentax mount than in other mounts.