This is my fix for the Industar-69 28mm 1:2.8 pancake lens famous infinity focus problem. I read several tutorials and pieced them together and came up with this non-destructive hack that still allows an infinity stop and close focus stop with only one minor setback of the aperture scale mark.
I used a digital camera for this fix which I suppose 90% of the uses for this lens is but, if you have an old 35mm film camera with the M39, Leica screw mount (with a hinged or removable back plate) you can use this lens too, just use a frosted glass plate of some kind, a removable SLR focus screen works good, or I’ve even used scotch tape pulled tight over the film guides to focus test lenses.
As mentioned above, leave the top stop-post and the post in the focus ring but remove the lower post.
The lens top won’t be pointing up, even before this fix because the depth of the mounting thread group is shallower than a standard M39 lens. This lens was originally on a Soviet CHAIKA half frame camera. The lens could also be mounted on an enlarger.
Here are a few images taken with this lens.
some milkiness to the original, fixed here (above)
(above) This led me to believe the elements themselves needed to be cleaned. Indeed, I removed the rear element and with my loupe, found tiny spider-web fungus on the rear element of the front group just in front of the aperture blades, (a usual spot) I cleaned it with a 50/50 mix of hydrogen peroxide and household ammonia (put some on a Q-tip, wet area, let set 5 min. wipe dry, clean with fresh water, repeat if nec.)
This is a fun little lens. It is said that it’s glass is modeled after a Tessar. Great quality and uber cheap. I got mine on eBay from the Ukraine for $28 with free shipping. I could have got it cheaper but you want sellers with good feedback from Ukraine and Russia.