Originally posted by rparmar But please recognise that some do care. One example I came across was an editor for a national magazine who needs accurate interior shots. They use the Pentax lens for that reason after trying the Sigma and saying "not good enough". They have done thousands of shots at a pro level. I guess I should take their opinion into account.
(Can't find the reference off-hand but it was on another web forum.)
Please read my No. 1 point. I am not trying to knock your favourite lens.
But the OP did ask "which is better optically".
No offence intended, but for that precision, you would not be using a DSLR but a medium or large format with tilt and shift. that is the only way to get accurate interior shots.
the perspective distortion alone from a DSLR would make the shots too difficult to manage without doing perspective correction in post processing, and in that process, the corners fall out in the crop anyway.
I have used the 10-20 for tons of interior shots, and that has never been an issue. In fact, I would be really interested to see a comparison of the 10-20, at 10mm but cropped to 12, compared to the 12-24 without cropping. I would be willing to bet the cropped 10-20 would be better than the extremes of the 12-24.
What is more important is the point made by
revinhood, the extra stop in terms of speed. I have often found myself inside an old dimly lit cathedral with the camera held against a post, or sitting on top of a pew for stability. an extra stop, yeah that might be of interest, but then again SR does a really good job too.