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12-25-2014, 03:39 PM   #1
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Help! Cannot AF with FA 645 35mm F 3.5 AL (IF) Lens

I am new to Pentax and was just received my Pentax 645Z for one day, I purchased a 2nd Hand Pentax SMC FA 645 35mm F 3.5 AL (IF) Lens from Japan before the camera, now found that the lens cannot AF by the 645Z, anybody have an idea? I did push-pull the ring on the lens to get it to auto focus mode, and the camera is able to control the aperture. I also tried by turning the screw on the rear of the lens, it does changing focus. However, the camera always show MF with this lens, so it seems the 645Z does not look at this lens can do AF and did not drive the screw to do AF with this lens.

On the other hand, the 645Z is doing AF well with the Pentax D FA645 55mm F2.8 AL (IF) SDM AW Lens come with it.

Any particular settings on the camera for the older lens?

12-25-2014, 03:50 PM   #2
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According to the specs it should work and one reviewer reports that it does. SMC Pentax-FA 645 35mm F3.5 AL [IF] Reviews - 645 Wide-Angle Primes - Pentax Lens Reviews & Lens Database

Standard steps:
reseat lens
clean contacts
recheck AF/MF setting
make certain the battery is fully charged
12-25-2014, 04:33 PM   #3
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It should just work. Try cleaning the contacts on the lens. It's also possible that something's broken in the af/mf clutch.

Adam
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12-25-2014, 04:51 PM   #4
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QuoteOriginally posted by Docrwm Quote
According to the specs it should work and one reviewer reports that it does. SMC Pentax-FA 645 35mm F3.5 AL [IF] Reviews - 645 Wide-Angle Primes - Pentax Lens Reviews & Lens Database

Standard steps:
reseat lens
clean contacts
recheck AF/MF setting
make certain the battery is fully charged
Did try all these! But still did not change on the camera that it only show "MF".

---------- Post added 12-26-14 at 07:53 AM ----------

QuoteOriginally posted by Adam Quote
It should just work. Try cleaning the contacts on the lens. It's also possible that something's broken in the af/mf clutch.
Tried cleaning, still same. The AF/MF clutch seems works well, and as I said, at AF, when turning the rear screw, the lens does able to change focusing. It just the camera does not see the lens able to have AF.

12-25-2014, 05:30 PM   #5
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QuoteOriginally posted by thomaskplee Quote
The AF/MF clutch seems works well, and as I said, at AF, when turning the rear screw, the lens does able to change focusing. It just the camera does not see the lens able to have AF.
Therefore the wiring that should normally tell the camera what the clutch is set to may be broken.

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12-25-2014, 06:46 PM   #6
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Probably the connection is broken or some circuitry issues. I will have to return the lens to the seller after the holidays, thanks!
12-25-2014, 08:21 PM   #7
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The FA 35mm works fine on the 645z. Since your camera is functioning, the problem is pretty clearly with the lens. That's really frustrating! So sorry this happened. Let us know how Pentax handles your service requirements.

- N.
12-25-2014, 08:24 PM - 1 Like   #8
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Put the 645Z into Live View mode, and see if you can autofocus the lens using the contrast detect AF function of the camera. (As opposed to the phase detect AF function that's used when you're shooting optically, no Live View.) I'm on my second 645Z because my first one was faulty. The camera worked fine in every regard, but it would not AF with any of my FA 645 lenses in phase detect mode -- trying to engage focus just did nothing at all, as if the lenses were all manual focus. (I knew the lenses were all fine from shooting with them for years on a pair of 645D's.) But in Live View contrast detect mode, all the lenses would autofocus fine. I exchanged the body for a different one 24 hrs later with my dealer, and the 2nd body worked perfectly.

Depending on your results testing the two AF modes, it may tell you whether it's more likely the lens or the camera body that has a problem.

12-26-2014, 12:37 AM   #9
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QuoteOriginally posted by Royce Howland Quote
Put the 645Z into Live View mode, and see if you can autofocus the lens using the contrast detect AF function of the camera. (As opposed to the phase detect AF function that's used when you're shooting optically, no Live View.) I'm on my second 645Z because my first one was faulty. The camera worked fine in every regard, but it would not AF with any of my FA 645 lenses in phase detect mode -- trying to engage focus just did nothing at all, as if the lenses were all manual focus. (I knew the lenses were all fine from shooting with them for years on a pair of 645D's.) But in Live View contrast detect mode, all the lenses would autofocus fine. I exchanged the body for a different one 24 hrs later with my dealer, and the 2nd body worked perfectly.

Depending on your results testing the two AF modes, it may tell you whether it's more likely the lens or the camera body that has a problem.
Thank you for your information, I just tried again with this lens on the LV mode, but it is the same, cannot AF. The camera show it is "MF" all the time, so, obviously, there is something wrong inside the lens that cannot communicate with the camera to tell the camera it is in AF mode. So I will return the lens to the seller after the holidays. I will buy another one later, as the price of this 35mm f3.5 is much lower than the 25mm f4, and lighter weight to carry.
12-26-2014, 02:22 AM   #10
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I have the same problem with the FA45mm, it works fine on the 645NII but does not autofocus on the 645D.
Since it is the FA45 (not worth to use digital) I did no further research.

-Linus-
12-26-2014, 02:26 AM   #11
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By the way, since I bought my 645Z from Japan, so it only comes with the Japanese user manual, is there some place I can down load an English user manual, as the Pentax official website do not have such available, thanks!
12-26-2014, 03:38 AM   #12
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Just google Pentax 645z manual. It worked yesterday for me. Sorry do not have link at hand.
12-26-2014, 05:03 AM   #13
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QuoteOriginally posted by thomaskplee Quote
By the way, since I bought my 645Z from Japan, so it only comes with the Japanese user manual, is there some place I can down load an English user manual, as the Pentax official website do not have such available, thanks!
645z Manual Download Link
12-26-2014, 05:21 AM   #14
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QuoteOriginally posted by vivavegas Quote
Thanks a lot!
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