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08-29-2011, 04:23 PM   #1
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K-5 and Sigma 170-500

I've had my k-5 for several months now. Today I finally decided to use my old Sigma 170-500mm f5-6.3 with it. I noticed that when in aperture priority mode the camera allows me to set the max aperture to 4.5 (@ 170) and 6.7 (@500) vs the advertised 5-6.3? This may be a dumb question but I am wondering why?


Last edited by apac; 08-29-2011 at 04:57 PM.
08-29-2011, 05:55 PM   #2
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Strange, but you are not the only one, check the the lens review section, others have reported the same with K-x and K10D.
08-29-2011, 07:57 PM   #3
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I believe the apeture range is coded in the contacts of the lens, it may be the contacts need a good cleaning. It does seem strange its .5 low at 170 and .5 high at 500. Have you tried it on another body?
08-29-2011, 08:32 PM   #4
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Apac, since you mentioned you've only had the K5 for a few months compared to the Sigma, am I correct to assume you've used the lens with a previous Pentax model? If so, did you notice this issue with those cameras or only with the K5?

If anything I think the lens is communicating the wrong info to the camera, or the camera is misinterpreting.

I assume the aperture ring is set to auto. Try switching it to manual (you have to turn the option in the menu to allow use of lens aperture) and see what the camera says when you manually set it.

08-30-2011, 05:44 AM   #5
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I don't have another body, digital that is. I have an old manual 35mm body that I use the aperture ring to set the aperture.

Yes, when this happens I have the aperture ring set to Auto. I will try cleaning the contacts as well as switching to manual and see what the camera says tonight after I get home from work.

Thanks for for your replies.
08-30-2011, 04:18 PM   #6
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I cleaned the contacts and that did not help.

I had already enabled the use of aperture ring on my camera settings. I set to manual but camera always shows "F--" .
08-31-2011, 04:10 PM   #7
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My experience with some older Sigma lenses is that their quality control isn't what is is today. It's perfectly possible that the lens actually performs as your K-5 reports. As long as you can rely on the lens to take decent photos, it shouldn't be a big deal.
08-31-2011, 05:01 PM   #8
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QuoteOriginally posted by mysticcowboy Quote
My experience with some older Sigma lenses is that their quality control isn't what is is today. It's perfectly possible that the lens actually performs as your K-5 reports. As long as you can rely on the lens to take decent photos, it shouldn't be a big deal.
Agreed... It is more curiosity than anything else. I was hoping there would be some sort of reason why this is happening... Thanks.

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