Exakta Lens Mount Question

[Univer]

Hi All,

Apologies in advance for what I'm reasonably sure is a dumb question.

I don't have a lot of experience with Exakta lenses. I briefly owned one of the Varex models, many years ago, but I don't believe I ever owned any additional lenses for it.

Now that I have access to a micro-4/3 camera (and an Exakta adapter), I've been picking up a few Exakta-mount lenses here and there. Most of them mount just fine on the adapter, but some are a bit more balky.

Last night I tried a lens - a Komura 135/3.5 - that wouldn't mount at all. It seemed that something was physically preventing the lens from rotating far enough to allow the spring-loaded catch to grab its locking pin. And the issue wasn't just with the adapter; I had the same problem with a vintage Exakta extension tube that I tried, by way of troubleshooting.

Not knowing what else to do, I unscrewed the little pin that projects from the side of the mount (not the locking pin; the pin I'm talking about is tucked under one of the mount flanges, and is at 90 degrees to the axis of the lens). Sure enough, with that pin removed, the lens mounted perfectly on both the adapter and the extension tube, and seemed stable and secure once mounted.

I did a quick check of the few Exakta lenses I own, and discovered that most of them had this pin, but some didn't.

My question: what's the purpose of the pin? And in light of the fact that some lenses seem never to have had it, is there any reason to be concerned about removing it?

Thanks for your help!

Cheers,

Jon

[woodrim]

I have an exacta mount Komura, but I don't know what the pin is that you are describing. There is one very small screw that locks the threaded mount in place on mine, but that wouldn't be involved in any mounting effort. Before I butchered the mount, I do remember seeing a very tiny screw actually in the bayonet; perhaps that's what you are describing. In any case, and especially with a pre-set lens, there would be nothing functional involved with the mount other than mounting, so if you can make it fit to your adapter, I think you're ready to go.

[std]

Hi Jon
can you post a picture of how this pin looks like.

I had and still have some exakta mount lenses and use them on my Olympus e-p1, but never had any troubles mounting a lens.
Maybe the ones you have are slightly different from the original exakta mount.

[Univer]

Hi,

@std: I don't have the lenses at hand, but maybe a couple of borrowed images (one from Rick Oleson's lens-mount-ID site, and one from MFL colleague overmywaders) will help. They're not optimal, because they're not intended to highlight this little screw, but it is visible, peeking out below the bayonet flange, in both images:





@woodrim: yes, I'm talking about the small screw/pin that protrudes from the bayonet itself. I'm not concerned about any functionality in communicating with the camera, but I wonder whether it's some sort of second locking device, intended to engage the flanges at the "bottom" (i.e., closest to the camera) of the lens-mount throat. (Even if it is, it may be that, for my purposes at least, the lenses are adequately secured by the primary locking pin and the spring-loaded catch.) If you don't have an Exakta camera or adapter in front of you, it may be difficult to visualize what I'm talking about.

Honestly, I would expect to find some variation and awkwardness in trying to get these various lenses and adapters to cooperate. Exakta lenses were made for decades, by dozens of manufacturers, and it's not shocking, perhaps, to discover that an early 1960s Japanese Exakta-mount lens doesn't mount with 100% precision to a c.2010 Chinese adapter. One is dealing with all kinds of manufacturing tolerances, old and new, to say nothing of years of wear. I was prepared to attribute the occasional issues to those factors alone, and I was a little bit surprised to discover that removing this screw fixed the problem, for this lens at least.

Cheers,

Jon

[luisalegria]

I have some Exakta mount lenses and also some T-mounts with this screw. I think it may have been common on some later lenses. I think it may be there to prevent the lens from turning clockwise in the mount, and disengaging from the catch, as some of the locking catches on on some Exaktas may be less effective in preventing clockwise rotation than counter-clockwise.

[Univer]

Hi,

Sorry to dredge this thread back up; I had completely lost track of it.

Thanks, Luis - I was hoping you might pop in. Your explanation makes perfect sense. I think I'll proceed on a case-by-case basis, leaving well enough alone where the bayonet screw presents no issue, and testing to see if removing it improves matters where a lens is balky about mounting to my adapter.

Cheers,

Jon