Originally posted by donesteban Well, it is a bit sad. Especially if you got one of the DFA from Japan and are using both film and a 645D or Z. When using a film body, it gives a much wider view again, so you basically have two primes in one. The 28-45 might be sharper, especially wide open, but is not fully covering 41x56mm
Pentax can either continue making full frame lenses that may or may not be useful in the future, or optimize the optics for better performance today, kind of a trade off going on here.
With a telephoto lens this isn't as much of a problem, since you're not losing a lot of performance, but in a wide, they could easily make the lens wider, have a larger aperture, and smaller/lighter all at the same time by catering to 33x44. The hood will also cover the correct framing.
While the 25mm wasn't outright bad and many people did make good photos with it, you can say that a lot of wide-angle lenses for a lot of systems aren't bad either, meaning that with the Pentax system all you're getting are the bonuses offered by the improved sensor tech. Pentax needs to get that every new lens has to push the limits of the sensor so that the system as a whole would be more desirable, rather just for getting that one extra stop of DR over a D810.
For instance, the Sony/Zeiss FE 35/1.4 is an awesome lens even used wide open, and the A7RII is a spitting distance away from the performance offered by the 645Z. Why doesn't the Z have something like it? A 45mm f/2 lens would be very welcomed by many I can imagine, certainly by me.