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07-07-2019, 10:26 AM   #1
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HD Pentax-D FA 645 35mm F3.5 on manual cameras

The review for the HD Pentax-D FA 645 35mm F3.5 (over here HD Pentax-D FA 645 35mm F3.5 AL [IF] Reviews - 645 Wide-Angle Primes - Pentax Lens Reviews & Lens Database) says "The lens has an aperture ring which makes it fully backwards compatible with 645 film cameras."

I want to use this lens on a dumb adapter, so the statement (above) is promising. However, I'd appreciate confirmation that I could actually focus the lens on a dumb adapter. I know it has a manual focus ring, but contemporary focus-by-wire lenses often need power to focus. Some of the earlier autofocus lenses, perhaps like this one, had a mechanical clutch that allowed actual manual focus without power.

So, can this lens be used on a totally dumb mechanical adapter (no power, no contacts)?

Thanks in advance, Rob.

07-07-2019, 10:55 AM   #2

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If it's DFA, that means it is compatible with the digital Pentax 645s as well as the film ones. The film ones only used screw-drive focusing, not focus-by-wire, so it will be able to be focused manually.

Edit: Actually, DFA might not mean that about the focus mechanism, but on the Ricoh site is says it is "Body AF", which means it is the screw-drive AF mechanism used on the film 645s, so it is not focus-by-wire.

And here it indicates that all D 645 lens can be focused manually:

Last edited by leekil; 07-07-2019 at 11:17 AM. Reason: Adding info
07-07-2019, 11:57 AM   #3
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There are no 645 adapters with contacts to begin with- only ones with the aperture lever.

So, the only sacrifice that's made with a completely dumb adapter is a fully manual aperture diaphragm. You'll be able to focus the lens just fine.

No 645 lenses currently focus by wire.

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07-07-2019, 12:34 PM   #4
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Superb, thanks for the quick responses folks. That's precisely what I needed to know!


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