Mamiya Sekor-C 180mm - explain the buttons please

Hi, just bought the Sekor C 180mm 4.5, and need help understanding the buttons (I can't find a manual anywhere, and my Youtube searches have not answered the questions either)...

There are two buttons (see photos below) if you ignore the DOF preview button - I need to know what I use them for. The one alternates between M and X (first photo) and the second alternates between M and N where I presume the M stands for 'manual', and it appears to be a cable release socket.

Much appreciated!

P.S. if anyone can direct me to a manual download for this lens specifically, that would be fantastic

M/X is the flash sync. Leave it on X unless you're using flash bulbs.

M/N is for Mirror lock up and Normal.

cramej said:

M/X is the flash sync. Leave it on X unless you're using flash bulbs.

M/N is for Mirror lock up and Normal.

Click to expand...

Much appreciated! My only other lens, the 90mm K/L makes the assumptions for you - if there is a cable in, it is in the alternative mode. So neither of the ports are accompanied by switches

Both the M/X switch and the mirror up operation are explained in the RB67 camera manual.

M/X switches are extremely common on lens shutters made up until some time (maybe the early 1970s or later).

I don't think there were specific lens instruction sheets, they're at least not as common as the overall "Mamiya Lenses" instructions. These would change based on things like floating focus elements, which weren't on the 1st generation of the lenses that use those IIRC.

But as others have said, the Main RB manual has all you need to know about lenses, and it's on the Butkus site.

Also, Bob Shell's "Mamiya Systems" hardcover is usually easy to find used - there's a some cheeseballery photo-wise, and his filters chapter has some howling errors, but it's a good overview of the RB, the original RZ, the Super and Pro 645 and a TLR. The systems charts are there and they're handy of you eder need an accessory part number.

Actually, there are instructions:
https://www.cameramanuals.org/mamiya_pdf/mamiya_rb67_interchange_lenses.pdf
If you make use of these, consider sending Mr. Butkus his requested donation.