Patrick, I don't have either lens. You may already know this, but here goes anyway. The PhotoZone survey for the Tamron has input from 6 users for 35mm film and 13 for APS-C dSLR; these two data sets are very consistent and rate the lens quite highly for optical performance. The same PhotoZone database has input from only 3 people so far for the -DA, so it's not yet reliable (the combined set of 19 Tamron users is likely to be more reliable). Fred Miranda reviews from 16 users also rate the Tamron very highly, but most are probably dSLR users (you can read the individual reviews to sort that out). You won't find any Pentax data at Fred Miranda; it covers C*n*n, N*k*n, and the Big 3 (Sigtamkina).
On the other hand (and on the *istDS), the 16-45mm is a wide to short-tele zoom (equiv. to 24-68mm on a 35mm film body), while the Tamron is a wide to normal zoom (about 26-53mm). If both are good performers (and I don't know about that) then you might want to consider the choice as being between ultra-wide for the film body vs. short-tele for the dSLR. PhotoZone raw scores at: www.photozone.de/active/survey/querylens.jsp Fred Miranda reviews at: www.fredmiranda.com/reviews/ Jim www.jcolwell.ca
