the Pentax is sharper but has more falloff wide open. the Sigma has slightly more chromatic abberation, but not as noticeable as my FA* 24 f2. for the *istD alone, i would choose the Pentax. if i had to use it on a film camera too then the Sigma is the better choice. the 15-30 uses an 82mm filter and still vignettes on the *istD. however, the loss is small enough that i was willing to crop out the filter edges. there isn't any point in using a filter on the Sigma with a film camera unless you are shooting very close to the 30mm end of its range. the Sigma is soft wide open and tightens up after closing down 2 stops. however, it never reaches the sharpness of the Pentax. it's not bad, but it's clearly not as good. on the film camera, it's not as noticeable.
Herb... ----- Original Message ----- From: "Bruce Dayton" <[EMAIL PROTECTED]> To: "Herb Chong" <[EMAIL PROTECTED]> Sent: Tuesday, March 30, 2004 10:43 AM Subject: Re: Sigma 12-24 > Thanks for the update. How well do you like your 15-30? Enough > difference between it and the 16-45 Pentax to choose it again if you > had the opportunity?
