Difference between Pentax K and KA mount?

AgX

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Apr 5, 2007
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29,973
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Germany
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I just checked the fit of lens-side K mount on a Pentax body with autofocus mount. Seemingly not only the automatic diaphragm, but also open aperture metering works (I'm just looking at the actuators).

The lens-side mount is a Adaptall-2 mount and Tamron state that for an AF camera one needs instead the KA mount (of course not transferring AF information).

What am I overlooking?
 
Last edited:

BobD

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Dec 22, 2006
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California,
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Yes, automatic diaphragm and open aperture metering work with regular K-mount lenses. So, does aperture-priority auto mode. KA mount adds support for shutter priority and program modes. KAF adds AF support.
 

Tomwlkr

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Aug 31, 2023
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SE Coast of NC
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KA lenses aill work in Program mode on Pentax and Ricoh cameras, I have a Pentax 50mm 1.4 KA on my Ricoh XRP now.
 
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