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12-14-2009, 10:09 AM   #1
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Anyone know about this one??

Does anyone have any experience with this particular M42 to K-Mount adapter?

Metal Mount M42 to Pentax PK Mount Lens Cam Adapter - eBay (item 260521318860 end time Jan-08-10 23:21:24 PST)

It would appear to be a logical approach to using an older screw mount lens on a modern camera as opposed to the more clumsy genuine Pentax adapter which has to be removed from the camera in a two step operation.

Anyone have any experience or thoughts?

Thanks in advance.

12-14-2009, 10:27 AM   #2
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I believe that you would lose infinity focus with any adapter that has a flange when mounting M42 on K-mount. If you have noticed, the official Pentax adapter fits completely inside the K-mount, so the back of the M42 lens sits flush with the K-mount. I believe it has to be that way because the registration distances (distance from lens mount to sensor) did not change from Pentax M42 days to the current K-mount.
12-14-2009, 10:29 AM   #3
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The adapter with the flange like this one won't allow infinity focusing.
12-14-2009, 10:29 AM   #4
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Don't - it will not focus to infinity. M42 and Pentax K-Mount have the same flange focal distance of 45.5 mm, so only adapters that do not change this will let you focus to infinity. This one clearly adds about 1mm to focal distance, so stay away.

I got a screw-in for my K-x that works fine - besides some moments of panic when it is stuck again.


12-14-2009, 10:41 AM   #5
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you can also buy an official adapter directly from the pentax website for $30 plus tax/shipping - I think most who have used it will say it is worth the price.
12-14-2009, 10:46 AM   #6
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These are really handy for things like macro bellows and such: (infinity focus is not a concern, there) ....and there's less to go wrong than with a knockoff of the genuine inside-the-mount adapter, (instead of those, just get the real thing) but as noted, you do lose that infinity focus.

Also, if you get one, be sure and clean the threads: the machining isn't always so tidy. But for what they do, they're a nice elegant solution.
12-14-2009, 03:02 PM   #7
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Thanks, everyone, I was not aware that they were back in stock on the Pentax site. I had looked there and had not been able to find them. What I did is to talk to Support via the Live Chat and was given the item number and the order page for it. In case any one else needs one here's a link to the item page:

PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)

Hopefully that will be useful to someone else also.

Now the question will be is it possible to turn that flange down on the other and use the lens that way??????

Thanks again everyone and Happy Holiday Season.
12-14-2009, 03:53 PM   #8
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the problem then becomes having the mount stay put. With the flanged adapter you have, there is a detent hole for the normal camera locking pin. The official Pentax adapter has a little spring.

About the only things these are good for is macro where infinity doesn't matter and if you're into converting other brand lenses to fit your Pentax K-mount. You can remove the original mount, adjust register distance to match Pentax, and fasten these to the altered lens, but that's a whole different subject.


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