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05-16-2018, 04:38 PM   #1
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645Z will not adjust aperture

Hello,

First post on the forum so I hope that this is the correct place. I have had a Pentax 645z for a number of months (purchased used) now and absolutely love it. I have been using the 645 fa 45-85mm, 120mm, and 67 105mm lenses with no issues. However, I just recently purchased a used Pentax-d fa 55mm 2.8 lens and noticed that the exposure was severely off when when taking photos. Putting it in aperture priority mode, manual mode, etc., does not help the issue. When doing mirror up, or taking a photo, I noticed (when looking in the lens) that even when I set the camera at f2.8, its appears the lens is always set to f22. I have tried resetting the camera, re-mounting the lens, etc. I don't have a clue if it is the lens or camera causing the issue. Has anyone else experienced this?

- Skyler

05-16-2018, 04:42 PM   #2
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Sounds like there is a mechanical problem with the lens, as the lever that operates the aperture isn't affecting the diaphragm.

If you move the tab on the back of the lens with your finger, does anything happen?

Adam
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05-16-2018, 04:49 PM   #3
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QuoteOriginally posted by Adam Quote
Sounds like there is a mechanical problem with the lens, as the lever that operates the aperture isn't affecting the diaphragm.

If you move the tab on the back of the lens with your finger, does anything happen?

Thank you for the reply Adam,

I am not near my equipment right now, but if memory serves me correctly, I could move the tab on the back of the lens and see the aperture smoothly changing. Though I will verify when I get back home later tonight.
05-16-2018, 04:54 PM   #4
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QuoteOriginally posted by Skyler89 Quote
Thank you for the reply Adam,

I am not near my equipment right now, but if memory serves me correctly, I could move the tab on the back of the lens and see the aperture smoothly changing. Though I will verify when I get back home later tonight.
Interesting. Since your other lenses work fine, it seems unlikely that the camera would be to blame.


Adam
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05-16-2018, 05:03 PM   #5
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QuoteOriginally posted by Adam Quote
Interesting. Since your other lenses work fine, it seems unlikely that the camera would be to blame.
Well, I suppose the issue is that you adjust the aperture on fa lenses manually (via a ring on the lens, but the lens has autofocus, so its not entirely manual), but I am unable to do that with the d-fa lens as it must be done within the camera. Unfortunately it is the only lens in my possession that cannot be adjusted manually. Thus, I am not sure if it an issue with the new lens (i.e., 55mm lens) or if this issue has always been present with the camera body.

Again, thanks for the help.
05-16-2018, 05:16 PM   #6
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QuoteOriginally posted by Skyler89 Quote
Well, I suppose the issue is that you adjust the aperture on fa lenses manually (via a ring on the lens, but the lens has autofocus, so its not entirely manual), but I am unable to do that with the d-fa lens as it must be done within the camera. Unfortunately it is the only lens in my possession that cannot be adjusted manually. Thus, I am not sure if it an issue with the new lens (i.e., 55mm lens) or if this issue has always been present with the camera body.

Again, thanks for the help.
What happens when you set the aperture ring on the FA lenses to "A"? If your exposure stops working properly, as with the D FA lens, then that would shift the blame to the camera.

In any case, I generally recommend avoiding aperture rings as electronic control allows for better precision and reduces mechanical wear.

Adam
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05-16-2018, 06:02 PM   #7
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QuoteOriginally posted by Adam Quote
What happens when you set the aperture ring on the FA lenses to "A"? If your exposure stops working properly, as with the D FA lens, then that would shift the blame to the camera.

In any case, I generally recommend avoiding aperture rings as electronic control allows for better precision and reduces mechanical wear.
You know what, I completely forgot that was a thing! Thank you so much. I will test it out later tonight and report what I find.
05-16-2018, 11:01 PM   #8
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QuoteOriginally posted by Adam Quote
What happens when you set the aperture ring on the FA lenses to "A"? If your exposure stops working properly, as with the D FA lens, then that would shift the blame to the camera.

In any case, I generally recommend avoiding aperture rings as electronic control allows for better precision and reduces mechanical wear.
Just got home and tested it. Turns out that it is an issue with the camera body.

Any recommendations on repair centers other than precision? Possibly KEH?

05-17-2018, 01:12 AM   #9
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QuoteOriginally posted by Skyler89 Quote
Just got home and tested it. Turns out that it is an issue with the camera body.

Any recommendations on repair centers other than precision? Possibly KEH?
I would probably go with Precision because they tend to be good with current gear, and feedback has been improving over the course of the past year.

But it wouldn't hurt to ask KEH either.

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06-12-2018, 02:34 PM   #10
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Update on everything, I ended up sending it to KEH as they were 1/3 the cost of precision. After a little less than three weeks I just got an email stating that it requires some tweaking to the software and as Pentax will not sell them the software, they cannot perform the repair.

This definitely sucks as I have spent over $100 to ship it to them, and now would have to spend another $100 + $800/900 for precision to repair it. I'll likely just use the older lenses and sell the d fa lenses as they are unusable. Spending that much to repair it doesn't make much sense to me as the price of the camera continues to drop.

I guess the moral of the story is to just send it to precision if it absolutely must be fixed. Now let's hope my camera comes back in one piece.
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