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12-23-2010, 09:49 PM   #1
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Tamron 17-50 - Unable to change the aperture

I mostly used this lens to shoot at 2.8 so not sure how old is this problem but I noticed it for the first time. I am unable to change the aperture using camera (in any mode). Aperture is clean and snappy so this is not a sticky aperture problem.

When I try to change the aperture, camera does not change aperture and stays at 2.8 in back LCD (k-x). However it shows the aperture change in viewfinder and changes shutter speed also - which is definitely not correct. Resulting photos are naturally overexposed. EXIF shows f2.8.

This lens got a water bath but then it was professionally serviced and everything works great at f2.8. Camera shows proper EXIF information etc so electronics seems to be working fine too. However, now service station says that partial electronics might be the problem.

Now, I am trying to understand, does electronic has any role in changing aperture? I thought it was aperture lever that controls the aperture (like in old A lenses). But may be I am missing something. There is absolutely no problem with cam since other lenses works great. Also, the this lens works great at f2.8, including focus, sharpness and EXIF information so I am not sure what's wrong.

Any help or inputs will be appreciated.

Thanks
Yusuf


Last edited by yusuf; 05-05-2011 at 08:19 AM.
12-23-2010, 10:32 PM   #2
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Hi yusuf,
I had the same issue after getting the same lens serviced for a focussing issue. Turned out they assembled the aperture lever incorrectly. Have a look at my thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/114628-tamron-...rexposure.html
12-24-2010, 12:14 AM   #3
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QuoteOriginally posted by d3zzzz Quote
Hi yusuf,
I had the same issue after getting the same lens serviced for a focussing issue. Turned out they assembled the aperture lever incorrectly. Have a look at my thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/114628-tamron-...rexposure.html
Thanks d3zzzz, I also suspected that but then I compared it with my 28-75mm and lever appears to be on the same side in both the lenses. Can you post the picture of lever after it was fixed?

Thanks
Yusuf
12-24-2010, 04:31 AM   #4
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Sorry, can't send you a photo of the lens right now since I'm not at home. But the lever is supposed to sit at the other end of the slot. But if the position is the same as with your other lenses your issue might be different. Does the lever move? Is it spring loaded?

12-24-2010, 04:41 AM   #5
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QuoteOriginally posted by d3zzzz Quote
Sorry, can't send you a photo of the lens right now since I'm not at home. But the lever is supposed to sit at the other end of the slot. But if the position is the same as with your other lenses your issue might be different. Does the lever move? Is it spring loaded?
No worries, pls do send when you can. Yes, lever moves and has spring action.

Can any 17-50 owner send me a picture of mount showing lever position.

Thanks
12-24-2010, 05:46 AM   #6
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Here a quick photo of aperture lever.
Mike
12-24-2010, 08:44 AM   #7
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QuoteOriginally posted by COULDBE2 Quote
Here a quick photo of aperture lever.
Mike
Thanks Mike but too small picture to make out anything, can you pls post bigger picture.

Yusuf
12-25-2010, 01:15 AM   #8
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Can any 17-50 post a few pictures of mount please.

Thanks

12-25-2010, 05:40 AM   #9
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yusuf,
Sorry for the mirco photo, Please check in the Pentax User Photo Gallery in the miscellaneous section. You will find a larger copy of the photo.
Safe Holidays,
Mike
12-25-2010, 08:06 PM   #10
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QuoteQuote:
Yusuf: Can any 17-50 post a few pictures of mount please.

Thanks
Yusuf:

Let me know if this is good enough--if not, I'll post some other angles.

12-26-2010, 01:11 AM   #11
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Thanks Jewelltrail, Mike.

I compared my 17-50 with the picture - mount and lever is as it should be. So lever does not seems to be the problem. Any inputs what could be the problem?
12-26-2010, 01:43 AM   #12
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QuoteQuote:
Yusuf: Aperture is clean and snappy so this is not a sticky aperture problem.
Mike:

How do you know the aperture is snappy? The 17-50, unfortunately, has no aperture ring. When the lens is dismounted, is the aperture fully stopped down?

JT
12-26-2010, 01:53 AM   #13
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Yes, it does closes fully when it is dismounted. I tried to operate lever manually with hand and there is no stickiness and moves very freely. Also, the lens was cleaned very recently - just a few days back so that further eliminates that possibilities. Let me know if I can check something else and let you know.

Does electronics has any role into this?
12-26-2010, 02:01 AM   #14
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When you slide the aperture lever, do you have both caps off, in the light, so you can make sure the aperture is opening and closing correctly?
12-26-2010, 02:09 AM   #15
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yes it does, that the first thing I did. It opens when I move lever to other side.
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