Originally posted by Alex00 What is your suggest for being the sharpest. Have you tried any??
yes. all 3 ultra-wide zoom lenses + some Nikkor lenses which I had before but I won't mention them as they are off-topic.
one of the things that I don't like about the Sigma is it's colour rendering, weak borders and corners at wide open. but it is good enough and can be great when you go past beyond it's shortcomings. price and 10mm could be quite tempting.
Pentax 12-24, as I mentioned before, it suffers from horrible CA at the wide end at wide open, and it is quite pricey. but it is one darn sharp and contrasty all over the focal length from f4 to f8. so it's price is warranted due to it's overall performance.
the Tamron is quite or somehow a better performer overall as compared to the Sigma. but there is something about it's rendering that I really don't like or rather find annoying. it is sharper but is still soft at the corners. colours for me are dirty. quite weak on the contrast which is what I don't want in a wide lens. but the 10mm and 24mm could be quite desirable for people with a more versatile lens or with a lens setup of 10-24 and 28-75.
at the end of the day, I had to choose between the 10-20 and 12-24, where which I ended up with the 12-24 due to luck and 1st preference. otherwise, I would had the 10-20 because I could had it within my budget. so in a way, I'm thankful that the 10-20 deal didn't materialize. I got myself what I wanted from the start, for a price that I would and could pay for.