Originally posted by sholtzma I'm still trying to decide whether to keep my Pentax 12-24, or replace it with either a Sigma 8-16, a Sigma 10-20 f3.5, or a Sigma 10-20 f4-5.6.
In any case, I had been checking out used versions of the 8-16mm and then was shocked to see the price new. Why would it have no warranty?
I haven't read through all the posts to see if anyone has given you advice, but here's my take on your choices:
1) The super wide-angle of the 8-16 is wonderful. It takes in almost as much left-right as my fish-eye. The IQ is more than one could hope. Major drawback is distortion at the edges, especially if the lens is not perfectly level, but that's true of any ultra-wide.
2) The 10-20 is much smaller, lighter, cheaper. Published tests suggest that the older variable-aperture version has better IQ, and it can be had for bargain prices (under $300).
3) 2mm difference in FL may not seem like much, but in WA it makes a significant difference. I could easily see the WA difference when I shifted from a 17-70 to the new 16-85.
If $ is tight, look for the older version of the 10~20. If you have the $, go for the 8-16. You'll be happier with either than with the 12-24.