Originally posted by countzero Ok. After a few hours of panic, I got it solved.
<<<<<<<<<<<
I put the lens (M42) back on,<<<<<<<<<<<<, overtook 3 more "resistance points" and the adapter had completed a 360 turn, thereby ending up in the "free to remove" position.
Just wanted to let you know, in case anyone else comes across this.
The items in question were a K10D, a Hama PK-M42 adapter and a SMC Takumar 135mm f/2.5
Moral of my story below: for a
jammed m42 adapter with Nikon D40...
Firstly, when fitting on, line up the adapter and body dots before twisting on. 2nd secure this setup by carrying on twisting (it's a bit tight) until it clicks in a pin from the body. Quite some angle....towards200-300 degrees before the body release pin clicks through and secures the adapter. 3rd, if adapter feels too tight to come off after use, try counterzero's, and my method. Read on for details below.
My experience is with a Nikon D40 and a no-glass M42 adapter from a UK eBay seller.
I know this is an old thread but thanks to counterzero's method of unjamming this, I fixed a similar problem just now. This time with a Nikon D40 dslr and a no-glass M42 adapter. I didn't count the 3 resistance points, but basically the lens and adapter went right round again, got the adapter/body dots lined up pressed the body release button at the body and off came the adapter/lens combo. Getting the dots lined up and pressing the release button are the key end points of course.
The Nikon is my goddaughter's and I bought her the adapter. I fitted it on and it would not come off. Because trying to twist the adapter off on its own, at least the first few times seemed impossibly tight. And by the way, trying to twist it off with the lens on, anticlockwise to line up the dots for release as per eBay auction instructions sometimes just twists off the lens, but not the adapter. Keep turning it clockwise to reach the lined up dots situation will do it each time.
Any damage: No, thankfully. Not visible physical damage nor actual shooting/metering/other functions damage, none. I tested it afterwards shooting with the kit lens on auto focus etc. And yes, the nikon/M42 adapter plus m42 lens combo does work now for my goddaughter. Not nearly as good as my m42 adapter/pentax ist ds combo though bcos the longer lens flange to sensor distance on the nikons does not allow infinity focus unlike the shorther distances for pentax and canon. Unless you get an M42adapter for Nikon that has the added glass (more expensive and light reduction due to the glass).
Thanks counterzero.
It would have been a trip to the camera shop + costs otherwise......
Limits of the above Nikon 40D/no-glass adapter setup. The 28mm wide angle lenses are practically unuseable as they won't turn enough to focus. The 50-55mm lenses will focus say 10-12 feet and below but not more. The 135mm can focus 'further'.......So, macro and telephoto work only it seems from my experience.
Moral:
if really serious about M42/dslr work, steer clear of Nikon due to lack of focus towards and including infinity focus. Do some research, and
get a different brand, preferably Pentax.