Quote: Even with a simple four-bar you could take off quite a bit of register distance req'mt. You would be giving up cheapness/speed but a mechanism design to take a 45 deg mirror and translate it within the ~42mm space req'd is trivial.
We haven't yet spoken about the protrusion that already exists on many lenses, but you could still design a mirror to move in the space req'd. It's just whether or not the result would be worthwhile.
(Heck you could even just translate the mirror).
So... translate the mirror where? Farther backwards? You know, where the sensor is supposed to be?
It's not even just the mirror. Fine, the mirror is magic and we can make it shrink when we want to shoot K-mount lenses. What are the K-mount lenses being mounted on? If it's the 645 mount, that's 25mm too far forward, you lose infinity focus. The only alternative is to have a mount at the proper register distance (where the mirror is supposed to be), which means that all your lenses have to have a smaller diameter than the 645 mount so that they can fit inside the throat of the camera.
The idea of putting short-register lenses on long-register cameras is patently unworkable, and every workaround has already been investigated in depth by the crowd who adapt manual-focus lenses (alt glass) to digital cameras. You can lose optical quality and get a longer focal length (glass-type adapters), you can modify the lens (expensive and only good for a few mm tops), or you lose infinity focus (non-glass type adapters). The main solution is that you buy a body with a shorter register distance - which is why mirrorless are popular in those crowds. That's why I keep talking about a 645 mirrorless as the only solution to this problem.
Originally posted by ElJamoquio In the thought experiment above we haven't yet imposed the requirement of being able to use both 645 and k lenses. It's possible of course but would be more complex.
Using 645 and K mount lenses interchangeably (via an adapter) was the original point of this discussion.
Originally posted by jon404 Back to the lenses. You know, that 645D sensor is smaller than the 'normal' 6 x 4.5 size (54x40mm, Mamiya Leaf Credo 80 back)... only 44x33mm (same as the Mamiya Leaf Credo 40 back, BTW). Larger than full-frame's 36x24mm, but not by much. Point is, you could probably use many of the K-mount lenses on the 645D without getting objectionable vignetting. Making an adapter would take a bit of engineering, to handle the flange distance, etc... but what a payoff if it worked. Would be fun to manage a rapid-development project to pull this off!
I suppose there's nothing stopping you from making a mirrorless K-mount camera with a crop 645 sensor, that would basically be the "645 mirrorless" I described.