Originally posted by Hello_Photo As to whether I would upgrade to the F/3.5 version? No. For landscapes, I'm usually at F/8 anyway. Also, when you consider that you only need 1/15 sec shutter speed to hand hold at 10mm with a static subject (even less with SR and concentration), the lure of a faster or constant aperture lens is lost on me.
You're right that if you already have the 10-20mm in variable-aperture, there wouldn't be a huge reason to upgrade. However,
if you are buying new, there may be reasons aside from cost. I recently ordered the constant 3.5 version over the "older" one (at a $180 premium) for three reasons:
- Sharper than the old 10-20 at the edges (depending on the test you read)
- I use the full range and manual focus sometimes, and that's a much brighter viewfinder at 20mm
- HSM w/ quickshift focus override for hyperfocal when you need it
Plus I already have some nice 82mm filters (CPL and NDs) for another lens, so the larger filter size is a non-issue for me, personally.
Edit: just thought I'd add that while the Pentax 12-24 is only slightly more expensive than the 3.5 Sigma, and known to be sharp - I happen to be
very wide-angle hungry (as my name would suggest). 10mm vs. 12mm on an APS-C sensor is a bigger difference in FOV than you'd think! (+12 degrees, in this case)