Originally posted by dboeren It will probably be f/4.0 is my guess. But if it's sharp from wide open then I'm willing to consider that (depending on price). I mean, we're already accepting the same sort of tradeoff on the DA* 60-250mm. It's an f/4.0, but some people pick it over the 3rd party 70-200mm f/2.8 options right? If I need more speed than that then I can always use a prime lens.
Edit: Instead of f/4.0, is f/3.5 possible (the old Pentax-A 35-105mm was a constant f/3.5)? That would be impressive!
Although the forthcoming DA* 5x zoom is still very much vapourware, given that it's a landmark on the world's least reliable road map, I expect it to be "inspired" by one the most renowned zoom lenses, the Zuiko 12-60. Scaled up to APS-C that would be 16-80 F2.8-4. An alternative inspiration might be the Zeiss 16-80 F3.5-4.5. However, given that this will be professional grade, I think F2.8-4 is more likely.