Is it possible to use Pentax K mount lenses on a Pentax 645 via an adapter? If so, what is the name and type of adaptor required?

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    \$\begingroup\$ I know you can go the other way, but K to 645 would be very odd given the image circle would be quite small on medium format film or sensors. \$\endgroup\$
    – Joanne C
    Apr 21, 2013 at 0:54

1 Answer 1


No. Even, if someone would build an adapter it could not possibly fully work.

One normally adapts a lens for a larger format to a camera with a smaller format. Going the other way, as you suggest, would place a lens with a small imaging circle compared to your sensor or film and result in clipped edges. other words you would only the center which kind of negates the purpose of a larger format.

The other number to pay attention to is the flange distance. You can bridge a gap for a lens that requires a longer one but mounting it too far makes such lenses not able to focus past a few centimeters or less than a meter. This would happen if you placed a K-mount lens in front of a 645 mount camera.

  • \$\begingroup\$ Thanks, I thought that would be the scenario. Appreciate the response and confirmation. \$\endgroup\$ Apr 21, 2013 at 1:37

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