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03-31-2011, 01:11 PM   #1
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Join Date: Mar 2011
Location: London Ontario
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Autofocus FA 645 150 2.8 on 645D body

Hi all

I am relatively new to Medium Format, just got a new 645D and the DFA 55mm lense, and am getting used to it. I have moved up from a Nikon D3s and primes set.

I bought a used FA645 150 2.8 (IF) from ebay and it was advertised as an autofocusing lenses on the 645D. However the 645D does not autofocus with this lenses. It goes into MF (manual focus) mode. Is there something I am doing wrong, or is the lense likely defective.


03-31-2011, 01:19 PM   #2

Join Date: Feb 2008
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Look on the lens barrel just behind the focus ring, if you don't see "Auto Focus" written on the barrel, the lens is set for manual. Push the focus ring towards the front of the lens (it may be stiff and take some force); the ring should slide forward toward the front of the lens and auto focus should be visible.

03-31-2011, 01:30 PM   #3
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Join Date: Mar 2011
Location: London Ontario
Posts: 2
Original Poster
That was it. Just learned something new. Thanks Tom. Besides feeling a little stupid I am very glad I found this forum. BTW love the image quality of this camera - certainly is a gigantic step up from 35mm.

Thanks again.

03-31-2011, 02:31 PM   #4

Join Date: Feb 2008
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You're welcome, glad that's all it was. I find Pentax's implementation of AF/MF very handy; if the AF isn't giving you what you want , a simple pull on the focus ring allows manual adjustment.
Now, post some examples.

04-02-2011, 12:28 AM   #5
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Join Date: Dec 2009
Location: Münsterland
Posts: 128
Pull the ring backwards

That's the way it should be...

I have a 645FA45mm that did well on the 645N & 645NII.
But now, with my 645D, it won't autofocus.
I hope Pentax will find out a reason for this strange behavior.


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