Originally posted by RGlasel The thing to remember about shifting this sensor is that larger dimensions increase the mass of the sensor unit enough that a more powerful system is required to move the sensor, especially if IBIS is to be as responsive as with smaller formats. If this more powerful system creates a lot more heat, that in turn requires further modifications. Why else would the HD 90mm (the most recent Pentax 645 lens?) have in-lens shake reduction? Combining supercharged IBIS with double the data per image and Pentax's 645 camera requires a giant leap in processing power and battery power (not even considering the higher demands of processing 100MP Pixel Shift images). After all the complaining about higher pixel density in smaller formats in order to get more megapixels, where is the visible benefit of 100MP over 50MP in a 44x33 sensor? Be careful what you wish for.
Well, I'd say 2 things. There's room in that Z box. The K1 managed both Ibis and PS with a 36mp sensor and the standard battery in one of the most compact FF OVF bodies out there. My battery life in that camera is pretty good. The point is well taken about the additional processing power required, but my Z's battery life is now excellent, so a drop to OK wouldn't bother me too much. And I'm not sure that the 90's OIS had much to do with heat----I think Pentax felt they needed to offer a stabilized alternative and that was the quickest way to go about it.
To the other point, I think that the Z's output is quite excellent and truly sufficient for so many purposes. But for certain things, and upgrade would be desirable, and those certain things happen to be things I do professionally and personally. But they are special cases, and in that rarified realm of such.
For me, it would be a tough call if it was an either or situation: "FF 645" at 100mp, no IBIS or PS, or "crop 645" at 100mp with IBIS and PS. Very tough call.....