Alan Chung wrote in message <349FD705.62D4@pc.jaring.my>...
>Mr 645 wrote:

>> I have a Sigma 18-35 mm zoom and it controls barrel distortion very well. I
>> prefer to shoot it about f8 for sharpest image quality, but even for interiors,
>> lines stay straight.

>I also have a Sigma 18-35mm but I beg to differ from the above
>findings. I have shot a fair number of indoor group photos with it at
>18mm, f8 (and also stopped down futher). A number of the photographs
>show so much distortion at the edges that people in the group
>photographs at the edge looks like they have gain an instant 50 pounds -
>I mean the face are flatten, widen and stretched. Nevertheless, the
>Sigma is still a very beautiful and sharp lens, provided I avoided the
>wider focal lengths for group shots.

I think you may be confusing two image characteristics, linear distortion,
and perspective characteristics... You can find more on these subjects
on my web page under "I babble", then "On Seeing and Perspective", and
"On Lens Distortion Types". BTW, I would have a hard time believing that
the Sigma 18-35 has low linear distortion at 18mm - but, oddly enough,
high linear distortion of the "barrel" type would actually reduce the
"distortion" you refer to...
--
David Ruether
http://www.fcinet.com/ruether
ruether@fcinet.com