Mir 1A lens

Hello again!

Several years ago, I had a 1973 M42 Mir 1A lens (2.8/37mm). I saw very little documents about it.

Optically, it seemed similar to any other Mir 1 but the aperture system was odd: only one ring to turn with a chrome button and a spring. To adjust the diaphragm, I needed to push the button and turn the ring. As soon as I released the button, the diaphragm was linked to the ring which was used as any preset lens (full aperture to preset aperture by turning it). If I wanted to go back to full aperture, I just had to push the button and the diaphragm was set to nominal aperture.

Now, the question: knowing that preset Mir 1 lenses were made since years, what was the specific use of such lens (if any)?

BTW, there is one to sell on Ebay (Item #360076906260): not really cheap ($80) for a Mir 1 but it is not the usual type...

Thanks for your comments!

Nicholas
Easy, remove the rear ring, so that it can be adapted (with the proper "A" ring to several cameras Zenit M39 Zenit M42 Zenit K Mount Kiev N mount and others..

LP

Yes luiz but it doesn't explain why they changed the aperture system; a regular preset one would be fine as there is no connection with the mount. Strange...

Nicholas
Noblesse oblige changement!
LP