About a year ago i bagged on the Ziess 18mm F3.5, well, even though i havent used it, i take my words back.
here is a photo using a Sigma 18mm F2.8 on a full frame camera, even at F5.6 you can see how quickly the image deteriorates in the corners/sides
the Sigma cost me 140 bucks, compared to the ziess price of around 1500 USD.
I expect that the Ziess will not exhibit such degradation, hence the price.
On digital however its a moot point, as most of that softness becomes hidden due to cropping.
Which i think everyone should keep in mind when talkinga bout Pentax's current DA lineup of glass. Its much easier to make optics that cover a small image circle with edge to edge perfection.
If the DA40 was constrcuted to fill a full frame, even at its current aperture size, and maintained its quality, i can assure you it would cost much more than it does now.
again, this is not OOF, this is edge softness.
Last edited by Gooshin; 03-02-2009 at 08:48 AM.