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02-04-2014, 03:38 AM   #1
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Tamron 28-75mm Problem

Hi all,

First post here. Photo newbie with a K30.

I've just received a brand new Tamron 28-75mm f/2.8 from B&H and I'm having trouble with the aperture. When I first mount the lens the aperture is wide open and when I take a shot it steps down to the desired aperture for the shot, this is the normal behavior for a DSLR no?

After taking the photo the aperture goes to about f/9 and stays there - any successive shots and metering are done at f/9 or something silly, despite what the camera screen shows for the f-stop. It appears as though the camera doesn't know what f-stop the lens is at as after taking a photo the EXIF shows the aperture selected in camera, not f/9. If I remount the lens I can take a nice photo again, but just once before the aperture shrinks again. Turning the camera off and on does nothing. Playing with the aperture ring doesn't help either, although I can control the aperture with the ring and manually expose until I put the aperture ring back on the "A" setting and take a shot.

I have the latest firmware. I've checked the aperture lever on the lens and camera and they both feel fine (springy) and the blades move freely. I don't have any trouble with my two Pentax lenses (18-55 and 35 f/2.4). This is a Japanese built lens.

Any ideas fellow Pentaxians?

02-04-2014, 04:13 AM   #2
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Hmmm .... Sounds to me as though the aperture actuation lever is acting up, but you say that the lever and the blades work smoothly when moved manually with the lens unmounted.

Are you able to try the lens on another Pentax body?

It's possible that the lever on the lens is bent slightly out of alignment, and it's catching somewhere on the camera side.
02-04-2014, 04:49 AM   #3
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Hmm the lever on the lens doesn't look bent but compared to my other lenses it sits further towards the center of the lens. Maybe they are slipping past each other?
02-04-2014, 05:07 AM   #4
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Did you buy the lens new or used?

If it's new, I'd suggest that you send the lens back for replacement. If used, then I might suggest that you try bending the lever towards the outer edge GENTLY. However, the usual disclaimer applies and you do this at your own risk.

02-11-2014, 07:15 PM   #5
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Join Date: Feb 2014
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Just to follow up on my aperture problem for those interested, I sent the lens back to B&H for refund and ordered a new one which I received yesterday. The shipping from NY to Tasmania is amazing, it arrived in 4 business days!

The new lens works completely fine - no aperture or focusing problems. It was either an electronics fault in the lens or an out-of-alignment aperture lever on the lens.

Last edited by trevor2; 02-11-2014 at 07:16 PM. Reason: Typo
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