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12-13-2010, 06:24 AM   #1
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PK Mount Help on Sigma Mirror Lens

Came across this 600 mm f8 sigma mirror lens at Craigslist Toronto for CAD 75. The rear cap is marked PK. Appears to have the K mount adapter fitted permanently and will not screw off the lens. The owner an elderly professor claims he bought it factory fitted. have attached (2) photos.
Request help and advice:-
a) Will this lens come off my K20D? I believe a K mount adapter remains on the body when the lens is screwed off. The adapter is then removed by depressing the spring and rotating it out of the body.
In this case we wont get access to the spring when mounted on the body. Of course I could try removing the spring clip with a jewelers screwdriver. In which case the lens may not not lock.
b) Is it truly a factory original installation as claimed by the professor?


Last edited by nanhi; 06-29-2011 at 08:09 AM.
12-13-2010, 06:53 AM   #2
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in looking at the second photo, it appears that there is a spring clip on the lens that blocks the adaptor from coming off. up can try unscrewing the adaptor by pressing that tab. As for the lens not coming off the camera, yes take the spring off because it will catch in the body.

once you get this apart, I recommend using a flanged M42 adaptor. Many mirror lenses focus past infinity any way so it will probably still focus to infinity with the flanged adaptor, and these don't have a spring, buit engage the lens locking pin. therefore if you mount a flanged adaptor, and set it in place using a thread locker (loctite) it will remain on the the lens. Thsi gives the advantage of shorting all the contacts gauranteeing focus confirmation.
12-13-2010, 07:34 AM   #3
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Thanks Lowell for your prompt and very useful reply. Yes this lens does focus past infinity. I will try and unscrew the spring clip and see if the adapter comes off. Thanks God I did not mount it on my K20D.
I think this Professor was not using the lens on a camera, but as a demo or something. Just that it was in such a perfect condition and the price CAD 75 was so tempting.
I will buy a flanged M42 to K Adapter any way as you suggested - costs USD 6 to 12. Also I can cut a slot on the lens flange for the body pin to lock on to the lens - being a master mechanic and a DIY helps.
12-13-2010, 07:49 AM   #4
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QuoteOriginally posted by nanhi Quote
Thanks Lowell for your prompt and very useful reply. Yes this lens does focus past infinity. I will try and unscrew the spring clip and see if the adapter comes off. Thanks God I did not mount it on my K20D.
I think this Professor was not using the lens on a camera, but as a demo or something. Just that it was in such a perfect condition and the price CAD 75 was so tempting.
I will buy a flanged M42 to K Adapter any way as you suggested - costs USD 6 to 12. Also I can cut a slot on the lens flange for the body pin to lock on to the lens - being a master mechanic and a DIY helps.
No need to do anything with the lens, the flanged adaptor has a 0.8mm flange that has a slot which engages the lens locking pin. For the proce it is the best way to go.

Happy hunting

12-13-2010, 07:51 AM   #5
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Your mount looks a little different from mine

I have the Sigma mirror 600mm and here is what the mount on mine looks like... I do not have that locking tab and the k-mount seems permanent. Of course it may have come from a different production run.










For $75 you really can't go wrong, but I hope you are aware that it's not an easy lens to use. Unless you have a ton of light you'll need a stable tripod, and it's DOF is razor thin.

Pat
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