It looks like it is a mechanical problem. It isn't.
As a matter of fact, all SLR cameras (with the exception of Pentax LX with the sports VF) feature a VERY poor eyepiece (aka ocular).
You may look at what is available,
even from Pentax, when following some of jogiba posts over there in the K-7 video quality thread:
Originally posted by jogiba Here it is with a 40mm Pentax XW eyepiece for visual use. It's 2350mm F10 and 1480mm F6.3 with Reducer/Corrector f/6.3 .
Originally posted by jogiba I think I will try my Celestron 9.25 with F6.3 focal reducer to get 1480mm @F6.3 with my K-7.
Now you get an idea about how much SLR eyepieces really suck. A decent ocular has a so-called "high exit pupil" which doesn't force you to press the eye against the VF at all. And it would allow full 1.53x magnification even at 100% coverage!
We don't get it because we aren't demanding it ...