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07-17-2009, 06:45 PM   #1
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Help: can't get lens to mount on new K100D Super

I'm pulling my hair out here and I hope there's someone who can help me get this working..

I just bought a K100D Super, in part because I thought I could use the zoom lens that I used to us on my old Pentax Program Plus (film SLR). The lens is a Sigma 35-70mm.

I line up the red dots and I can insert the lens in the mount but it only rotates about half way and doesn't click or lock. I've check the spec's again and, as far I can tell, this lens should fit this camera.

If anyone had suggestions, I'd really appreciate it.

07-17-2009, 06:51 PM   #2
Damn Brit

I'm not familiar with that lens I'm afraid. I'm not sure if this will do anything but if the camera is in AF, set the switch to MF and try mounting it again. It does mount ok on your film SLR still doesn't it?
07-17-2009, 07:11 PM   #3
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Original Poster
I've tried both AF and MF.

And, yes, the lens still fits fine in the old Program Plus.....

Thanks, though....
07-17-2009, 07:14 PM   #4
Damn Brit

Someone will be along with an answer.

07-17-2009, 07:32 PM   #5

I've got an old Vivitar I can't use on my K10. There is a shroud on the lens that isn't on most other lenses. It prevents it fom mounting on digitals. It works on my K1000 though. You more than likely can cut it off with a Dremel. I didn't bother because I have other lenses in that range that need no modification.
07-17-2009, 08:03 PM   #6
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Check this URL:

Dremel tool for lens modification - Pentax Forum

You'll see the shroud that has to be reduced to the standard size for Pentax mounts. The only critical issue is not to get a bunch of crud in the lens as you sand or file.

Compare the shroud with your other lenses.


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