Image quality with prime lenses (&what's a good ultra wide)

[danbachmann]

Unfortunately the Sigma EX 15-30 (and the even wider 12-24 and lower) don't have any filter threads!

[danbachmann]

Based on this (Sigma quality control), I've steered clear of the Sigma. I held in my hand the Tamron SP 17-35mm and Pentax FA 20mm in my hands... I should have got both... I settled for the Tamron SP 17-35mm. I expected it to be almost as good as my Pentax 28mm prime, but I find it quite soft when focusing on infinity.

My Tokina AT-X 28-70, Pentax A 28 & 50 are very clear. My Tamron SP 90mm is absolutely amazing in sharpness. I've read that ultra-wide angle zooms are difficult to design and that this is quite normal. Is this true? With so many people using 17-35mm lenses, it seems hard to accept. The images look pretty good, but when looking at them at 100%, they all lack the sharpness that my other lenses offer, unless the subject is very close to the lens. What is your experience on this?

I'm debating for travel photography if I should now leave the new 17-35 lens behind and stick with my 28mm prime. The 17-35 will still be perfect for indoor events such as weddings.

[AdrianW]

Unfortunately high quality ultrawide zoom design does seem to be presenting a challenge at the moment...

My Canon 17-40 f4/L is pretty good, but it's definitely not the sharpest lens I own - that honour goes to my Canon 100mm f2.8 USM Macro.

Whether the 28mm will suffice depends on the situation obviously. Personally I'd take both, but then maybe there's a reason I have a bad foot ;)