I'm afraid technically it might not be possible, hardware wise. Yet, it is just another example showing that firmware is not a miracle indeed, in contrast to what many users are thinking.
The aperture coupling actuator is a one-off stepping motor from the wide opened position to the stopped down position for the set f-stop. It is not a continuous moving stepping motor as designed (which will require even more torque and higher precision). As such, your dream might not be able to come true very possibly.
BTW, I don't find it is of any difficulty for the current optical preview facility as designed now. Actually, the Pentax's design is already very user friendly, for the position of the preview level. If you have a large and bright viewfinder Pentax DSLR like the K10D, it is already very good indeed.
On the technical architecture of the K-mount system and how it operates, you guys may read my old article of this:
K Mount Metering & Exposure Bases - A Technical Brief Originally posted by button Hello everyone,
I may have mentioned this in the past, but I think it bears repeating. Here is a firmware update/future camera feature request:
In optical preview mode, please allow continuous variability of aperture via the rear dial while holding down the preview lever.
As of now, you have to dial in the aperture, pull the lever, check it, then change the aperture again. This process takes entirely too much time when the moment presents itself, and could take maybe 1/10 time now needed if the above functionality were enabled. Firmware 1.31 anyone? Ben? Chris? Anyone?
John