Please help identify/mount oddly-threaded Nikon M Plans

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Chris S.
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Please help identify/mount oddly-threaded Nikon M Plans

Post by Chris S. »

In my quest for objectives to use on a bellows, I recently received from separate vendors two Nikon M Plan plans with identical threads that are distinctly bigger than RMS. This surprised me. Don't only later, infinity-corrected Nikon objectives have non-RMS threads? Web sources seem to state that the thread size changeover occurred simultaneously with the move from finite to infinity correction.

So two questions:

1 Can anyone tell me if I really have the finite objectives (210mm tube length) that I am supposed to have purchased?

2 If so, can anyone tell me how to adapt them to RMS equipment?

Details and pictures follow:

Lenses are marked as:
M Plan 2.5 0.075 210/0
M Plan 40 0.5 ELWD 210/0

Both lenses have threads that I measure at 25mm--but I don't have a caliper, just a tape measure. Online sources that I've found say that later Nikon lenses use an M25 mount, but a Thorlabs RMS to M25-0.75 adapter does not fit--seems a bit too small. Thorlabs makes an RMS to M27 adaptor, but I can find no mention online that Nikon has used an M27 thread. Would order one if there is reason to think it would work. Here is a link to the Thorlabs adapters--I bought an RMSA2, and wonder if I need and RMSA4:
http://www.thorlabs.com/NewGroupPage9.c ... N=81614800

On one lens, the barrel was screwed in very loosely, and I removed it for one photo below. If barrels are of interchangeable size (are they?), a lens could end up mismarked by having the wrong barrel. So I'm concerned that I might not have actual 210mm tube length M Plans.

One vendor said the lens came from a Nikon Optistation.

Pictures below (some stacking). Anyone wishing to add images to this thread is welcome to do so.

In advance, thanks for any input.

--Chris


M Plan 40x for 210mm tube--or is it?
Image

M Plan 2.5x for 210 tube--again, is it? Lens barrel unscrewed for photo--could a barrel switch cause lens misidentification?
Image

mgoodm3
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Post by mgoodm3 »

http://www.photomacrography.net/forum/v ... hlight=m26

I believe it to be a M26 thread. Edmund has adapters for M26. I have a M26 to Cmount adapter.

Chris S.
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Post by Chris S. »

Thanks, mgoodm3. I hadn't seen that useful thread, and probably wouldn't have thought it applied since they are talking about BD objectives. But now that I look it over, I see how you may be right.

Thanks also for the tip that Edmund has adapters in this size--the way they are labeled, I doubt I'd have found them. Oof, though--$80 for an M26 adapter, when Thorlabs has essentially similar M25 and M27 adapters for $20. Oh, well. I'll order one and cross my fingers that it lets me use these two objectives.

Cheers,

--Chris

Charles Krebs
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Post by Charles Krebs »

Chris,

The colored band indicates (a range of) magnification.

see near the bottom of this link:
http://www.microscopyu.com/articles/opt ... specs.html

The thread on these is the larger "BD" thread. Generally you find the the brightfield only ones like you have with the smaller RMS threads. But these could be used together (mixed) with BD objectives on on a microscope nosepiece with the larger hole size.

Chris S.
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Post by Chris S. »

Charles Krebs wrote:The colored band indicates (a range of) magnification.
Thanks, Charles. I should have thought about that, but didn't. So the colored bands on these objectives are perfectly consistent with the information on the barrels.
Charles Krebs wrote:The thread on these is the larger "BD" thread. Generally you find the the brightfield only ones like you have with the smaller RMS threads.
Positive ID much appreciated! So adapter suggested by mgoodm3 should do the job.

Joseph S. Wisniewski
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Re: Please help identify/mount oddly-threaded Nikon M Plans

Post by Joseph S. Wisniewski »

Chris S. wrote:In my quest for objectives to use on a bellows, I recently received from separate vendors two Nikon M Plan plans with identical threads that are distinctly bigger than RMS. This surprised me. Don't only later, infinity-corrected Nikon objectives have non-RMS threads? Web sources seem to state that the thread size changeover occurred simultaneously with the move from finite to infinity correction.

So two questions:

1 Can anyone tell me if I really have the finite objectives (210mm tube length) that I am supposed to have purchased?

2 If so, can anyone tell me how to adapt them to RMS equipment?
Of course I can tell you. I'm not sure how to tell you, because if this happened to me, I'd be frightfully embarrassed. You don't know how lucky you are.

You have two perfectly normal Nikon CF 210mm objectives with RMS mounts.

They are currently sitting in two genuine Nikon chromed brass RMS to BD (M26) adapters. You can see this from the end view.

Take the adapters off and you're good to go. This is better than adding another M26 to RMS adapter to counteract the first adapter.

And if you're willing to sell the Nikon adapters, I am in desperate need of at least one, and two would be wonderful.

I'm lucky, too, because I get to razz Charlie about not recognizing that those objectives were sitting in adapters.

Chris S.
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Post by Chris S. »

Apologies for the long overdue reply. I was camping, and splendidly disconnected from computers. Now, back to reality.

I had in fact become aware that these objectives had standard RMS threads on adapters--advice from a dealer in used Nikon microscope equipment. I'd even suspected it at first, but the adapters were on very tightly and had the appearance of being an integral part of the objective. And for me, twisting the living daylights out of a lens requires a bit of assurance that I'm not about to destroy something.

Once armed with that assurance, I had at the lenses with a pair of well-padded channel pliers. It took quite a bit of torque, but once the initial bond broke, the adapters easily and smoothly dismounted.

Had planned to--and hopefully soon will--post pictures of the adapters for future travelers.

Thanks, Joseph! I have sent Joseph a PM of thanks and discussion of selling him the adapters. Had planned to save them for future use or sale, but if Joseph needs them now, he can have them

Cheers,

--Chris

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