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Forum: Pentax SLR Lens Discussion 04-14-2018, 03:45 AM  
Adapting Altix lenses to Pentax K using an M42 adapter
Posted By antipattern
Replies: 6
Views: 1,299
I recently got hold of a few Trioplan 50mm 2.9 lenses. They all came in Altix mount, for which there are very few adapters out there, and none of them are for Pentax. I saw someone adapting an Altix lens to a Canon EOS camera using an M42 to EOS adapter. They simply filed down parts of the M42 thread until the Trioplan fit into the mount and then glued the lens into the mount. I thought I could do the same with a cheap and cheerful Chinese M42-Pentax knock-off adapter. I first removed the little flange locking the adapter into the camera. I would recommend doing that as they can get jammed in the camera, particularly if the Altix lens locks into the adapter very tightly.

Then I held the lens to the camera to judge where the Altix flanges hit the thread of the adapter and started filing down one section of the adaptert first. I only need to sand down less than 1mm, and I was able to slide and lock the lens into place, without needing any glue at all. Because I didn't find the photos on the original thread very useful, I thought I would put in a few pictures detailling the process.

Here's the lens and the M42 adapter:

Here's the view from the mount:

Here's where I filed down the adapter. It was sufficient to file down on one of the three flanges only:

You slide on the adapter on the thread and push the section you filed down last:

Et voilá - the adapter locks in with a slight wiggle and - unlike the method described on Vintage Lenses, the lens locks fairly tightly and I don't need any glue. It's completely reversible on the lens.

Here is the lens mounted on the K3. Unfortunately I wasn't very diligent which way the lens faced when mounting the adapter, so the aperture scale isn't pointing upwards but sideways. But that doesn't affect the usability.

And finally the bubble bokeh:

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