Another odd thread

[ray_parkhurst]

I ended up with a couple of 3M objectives for Olympus. I think these are microfiche objectives in a different mount vs the big "cone" mount of the others in the lot. At first I thought they were RMS mount, but indeed they are a bit smaller at 19mm, with what I believe are 0.75mm pitch. Anyone know of a standard mount that matches these? I checked the FAQ but I don't see any reference to smaller than RMS.

[ray_parkhurst]

This one seems to be stumping folks. I plan to do a "tape job" to mate these into RMS for a quick check to see if they are worth pursuing. Other 3M/Olympus objectives I've tested have varied a lot in IQ, coverage, CAs, etc so not sure what I'll find. There are some gems out there. I may do a writeup on what I've learned, which is not a lot, but may still be helpful for folks. I liked the cone-shaped objectives so much that I had Raf make an adapter to M42/M52. Some of those have extreme coverage so might be good for the MF/LF guys. One was so wide that it pointed out some reflections in my setup that I didn't know were a problem, and after flocking I'm getting better contrast across the board!

[Ichthyophthirius]

Hi Ray,

Zeiss Jena metallurgical objectives (epi-illumination; infinity tube length, pre-CF250) had an M19x0.75 thread. Though unlikely that it had any relation to our lenses.

Regards, Ichty

[ray_parkhurst]

Zeiss Jena metallurgical objectives (epi-illumination; infinity tube length, pre-CF250) had an M19x0.75 thread. Though unlikely that it had any relation to our lenses.

Thanks Ichthy. Seems Zeiss is to blame for the last couple of odd threads I came across. Last one was M24, also a Zeiss objective thread. Now I see several M19 adapters available from Raf and realize I should have checked there before writing here.

I did a quick tape job and screwed the objectives into a RMS extension to test them. Like the other 3M/Olympus objectives I have, they were a mixed bag for quality. The "35x" looked good at the center around 4x but even the corner of APS-C was degrading fairly badly. The "40x-2" was a big surprise though. At around 5x it had excellent IQ at center and corner, with low CAs. I am planning a 5x shootout sometime down the road and will include this one.

Now I have a new one. An eBay seller included a few freebie objectives with an order I made. They are Rolyn brand and have M16.5 with what looks like 0.5 pitch. I see some M16x0.8 available from Raf (D-mount cine standard) but no 16.5's. Tiny little lenses. Sounds like another tape job.