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04-13-2015, 07:35 AM   #1
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Rotational Slop on Bigma with K-3

Hi Folks,
Just received a used Bigma from B&H and noticed a small amount of rotation when the lens is mounted on my K-3. Pictures are fine as are focus and OS. Rotation is not related to and kind of stress in the body or lens. None of my 6 other lenses do this, including the Sigma 18-250. I don't have another K mount to try. The amount of rotation is quite small, I would describe it as a millimeter between two hard stops. The camera rotates back and forth and goes "tick tick" when it hits the stops. The only play is rotational. No side-side or gaps. I know Canons can have some play in the mount and be OK but I'm not a Pentax expert so I thought I'd consult the forum members here. Overall it seems OK but I'll admit I don't like it, feels fragile. I could get used to it if it's a characteristic of this set up. So I suppose my specific questions are (1) Is this a known issue for this lens, (2) Is it something I need to be concerned about? And (3) is this a characteristic of bayonet mounts in general, so if it happens again I won't worry about it.

04-13-2015, 07:44 AM   #2
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I do not remember anything like that when I had that lens. You might want to verify that the lens mount is securely fastened and the screws are not loose.
04-13-2015, 08:18 AM   #3
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QuoteOriginally posted by jatrax Quote
You might want to verify that the lens mount is securely fastened and the screws are not loose.

If there is any "slop", it should be limited to the clearance between the retention pin on the body and the corresponding slot on the lens. There is always a little.


Last edited by stevebrot; 04-13-2015 at 08:24 AM.
04-13-2015, 08:58 AM   #4
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Thanks! I checked the camera and lens mounts and they appear to be solid. Put the lens back on and looked closely and can see that the mounts aren't loose, they're just not locking together securely. I'll try to figure out if it's retention pin and the slot. Thanks again.

04-13-2015, 09:05 AM   #5
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I had that issue with my Sigma 500mm F/4.5. It started to effect how my camera was operating. I sent the lens off to a place in Arizona a couple of years back and they replaced the mount. It took over a month as they had to get the part from Japan.
04-13-2015, 11:03 AM   #6
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My 100-300f4 does that a little bit. I was concerned a bit at first but its so minute that I got over it after seeing how good it is.

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