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08-17-2017, 02:32 PM   #1
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Question about different Pentax mounts

I am looking at purchasing a Sigma 70-200mm f/2.8 EX DG APO OS HSM II, to utilize with my Pentax K-50.

However, there has been some cautionary language about this lens not being compatible with certain Pentax mounts in terms of of the autofocus feature.

One review states: "The HyperSonic Motor (HSM) focusing system promises fast, silent and accurate autofocus for users of all brands of DSLR, although Pentax users should be aware that this lens is effectively of 'KAF-3' mount specification, and therefore won't focus on bodies which don't support SDM lenses."

So...will this lens work with the K-50?

I called Sigma and Pentax, and there was a lot of fumbling and mumbling - not many straight answers. 😎

08-17-2017, 02:37 PM   #2
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Only some very early DSLRs don't support HSM. The lens will work fine on your K-50.
08-17-2017, 02:41 PM   #3
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On the older cameras they won't work, newer ones within the last few years (like the k50) will work fine with it
08-17-2017, 02:52 PM   #4
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QuoteOriginally posted by TXPentaxK50 Quote
I am looking at purchasing a Sigma 70-200mm f/2.8 EX DG APO OS HSM II, to utilize with my Pentax K-50.

However, there has been some cautionary language about this lens not being compatible with certain Pentax mounts in terms of of the autofocus feature.

One review states: "The HyperSonic Motor (HSM) focusing system promises fast, silent and accurate autofocus for users of all brands of DSLR, although Pentax users should be aware that this lens is effectively of 'KAF-3' mount specification, and therefore won't focus on bodies which don't support SDM lenses."

So...will this lens work with the K-50?

I called Sigma and Pentax, and there was a lot of fumbling and mumbling - not many straight answers. ��
Yes it will work. KAF3 lenses will focus on any Pentax DSLR from 2007 or newer, plus the K10D w/ 1.30+ firmware.

A simple way of looking at Pentax lens compatibility (which holds true with all K-mount cameras) is that the camera supports ALL lenses that were released before it. Most lenses newer than the camera will work as well, but this of course can't be guaranteed. In the K-50's case, all newer Pentax lenses also work.


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08-17-2017, 03:34 PM   #5
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There might be issues with the K-1 if the lens has the wrong identifier in firmware. Sigma can flash the firmware to fix it. But it should work fine on a K-50.
08-17-2017, 05:30 PM   #6
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Great info. Thank you so much !
08-19-2017, 07:26 AM   #7
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I bought one used from adorama a couple of months ago. I've only had time for test shots 😞 with my k30 and k3. So far so good! I'm guessing some new k1 owner traded it in.
But this makes me wonder if it will also be compatible with the kp, or the probable "k3mk iii"? I'm interested in replacing the k30 with a kp as the price has fallen. I like the sigma so far, specially for the price.

Anyone has the sigma-kp combo?
08-20-2017, 04:28 AM   #8
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QuoteOriginally posted by Caribe Quote
I bought one used from adorama a couple of months ago. I've only had time for test shots 😞 with my k30 and k3. So far so good! I'm guessing some new k1 owner traded it in.
But this makes me wonder if it will also be compatible with the kp, or the probable "k3mk iii"? I'm interested in replacing the k30 with a kp as the price has fallen. I like the sigma so far, specially for the price.

Anyone has the sigma-kp combo?
Sigma usually updates their firmware for use with newer cameras. At worst you'd have to send the lens in.

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