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06-08-2018, 12:27 PM   #1
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Tamron 28-75 lost aperture communication

I noticed my 28-75 was always showing as being at f/2.8 in EXIF and -- on the display the other day. I tried all kinds of things like using it on another camera and switching out of A mode but nothing helped.

I took a closer look and I think it lost a contact somehow. Here's a photo.
Can any of you confirm that this looks like a contact is missing compared to yours?

Any idea on how I might fix it?

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06-08-2018, 01:15 PM   #2
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Perhaps the auto-aperture pin (that extends when the aperture ring is set to A) doesn't extend as it should? It's the only thing that I can think of, since Pentax lenses do not communicate the selected aperture electronically.
06-08-2018, 03:14 PM   #3
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Yeah, maybe. Thanks for the suggestion. I'll check when I'm back home.
06-08-2018, 03:46 PM   #4
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All the contacts are still there. I've seen a few little niggles with non-Pentax lenses and auto aperture settings. I'd start by cleaning the contacts gently, then move onto other ideas. If you've got access to another body, that would rule out certain possible faults.

06-08-2018, 05:05 PM   #5
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I have the same issue with my F 50 1.7....It was working nice with my K5 and then with K1-II as well. Now aperture not communicating with both. Not sure what to do.
06-08-2018, 05:17 PM   #6
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QuoteOriginally posted by HarisF1 Quote
All the contacts are still there. I've seen a few little niggles with non-Pentax lenses and auto aperture settings. I'd start by cleaning the contacts gently, then move onto other ideas. If you've got access to another body, that would rule out certain possible faults.
I do and it is the same on both bodies.
06-08-2018, 09:36 PM   #7
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QuoteOriginally posted by mattb123 Quote
I noticed my 28-75 was always showing as being at f/2.8 in EXIF and -- on the display the other day. I tried all kinds of things like using it on another camera and switching out of A mode but nothing helped.

I took a closer look and I think it lost a contact somehow. Here's a photo.
Can any of you confirm that this looks like a contact is missing compared to yours?...
The contacts shown in your photo appear the same as on my lens. The groove on the bayonet ring shown at the bottom of the photo appears to be damaged. The groove is supposed to engage with the spring loaded lens release pin but failure to engage the lens release pin should not cause the issue you described.

Out of curiosity, please try the following test with the lens mounted on your K-1.
  1. Set menu "C-26 Using Aperture Ring" to "Enable."
  2. Set the exposure mode to "M."
  3. Turn the lens aperture ring to "8."
  4. While looking through the optical viewfinder, turn the "Off/On" switch to the aperture icon position.
The viewfinder should darken. If it does not darken, there is definitely a communication issue between the lens and camera. If you purchased your lens from an authorized U.S. retailer, you have a six year warranty.

Regards...

Dennis

Last edited by Kelvin 5500; 06-08-2018 at 11:25 PM.
06-08-2018, 10:47 PM   #8
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my lens looks more less the same.
have you tried to wiggle the lens in the mount?

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06-09-2018, 01:33 AM   #9
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pins look fine, also my lens has one position without brass
06-09-2018, 10:51 AM   #10
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Try cleaning the contacts (camera and lens). Try repeatedly taking in and out of "A" mode - if there is oxidation or dirt on the internal contacts this may clear it. Try moving moving and twisting the lens while mount - pin alignment may be slightly off though the spring contacts help to minimize this.
06-11-2018, 08:50 PM   #11
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I just checked my lens and you haven't lost a contact as others have noted. It does look like you have a build up of dust or other grime in the groove just below the screw. It is hard from the angle and lighting to see if anything is up with the aperture lever. It doesn't look quite right, but that may just be a distortion of the image. Feel free to post more photos if you are still having problems.

---------- Post added 06-11-18 at 11:53 PM ----------

Also, you mention switching out of A mode - can you manually stop the lens down? Does the camera recognize this?
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