Macroscope: Nikon MXA20696 2nd objective Lens in SK Housing

[Craig Gerard]

Nikon Part # MXA20696 '2nd objective Lens' in Schneider Kreuznach housing for use in an Infinity-corrected Macroscope.

I've been collecting the pieces for this setup for some time, and with the help of some friends in the USA, I have been able to acquire the final components.

Starting from the top:

1) M42 to Nikon Adapter. This connects directly to a Nikon PB-4 bellows.

2) Schneider Kreuznach M42 to 'V' Mount adapter.
The 'V' mounts were the most difficult parts to adapt as they are a proprietary SK design and will only play well with compatible pieces; but you quickly learn to appreciate them.

3) Schneider Kreuznach 25mm 'V' Mount extension tube.
The Nikon '2nd Objective Lens' (tube lens) Nikon Part # MXA20696 is positioned inside the 25mm SK extension tube. It fits nicely and sits on a 'ledge' inside the SK tube. 'Grub' screws lock it in place.

4) Schneider Kreuznach 6mm 'V' Mount extension tube.

5) Schneider Kreuznach Unifoc 12 Focusing Helical. It permits fine adjustments with a displacement of up to 12mm.
I'm not sure if this piece is neccessary but I just happened to have one so included it in the arrangement. I would not have intentionally purchased this piece.
I do not see it as a critical component, but it adds additional functionality and a touch of 'class' to the arrangement.

6) Schneider Kreuznach 'V' mount to M42 to adapter.
This connects to the jinfinance iris assembly via the internal threads of a 52mm to M42mm step ring.
I could not find an M42 coupler with internal threads, may need to have one custom made?. Still working on this area....I just had an idea involving some pieces from a set of Nikon K extension tubes

7) Iris assembly. It accommodates various, flat adapters to suit a range of microscope objectives.

I have a 75mm SK 'V' mount extension tube standing by for altering the position of tube lens relative to objective if required.

If intending to place a circular polariser/analyser in this configeration, where should it be located?



More details and results to follow.....

Total height 85mm.



Unifoc 12 @ full displacement.




Craig
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To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[Pau]

[Craig Gerard]

Thanks Pau,

Yes, I have a microscope analyser.

Would you consider any benefits in using a high quality circular polariser as an alternative?


Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[Pau]

Craig,
Just to add a point to my former fast reply:
Because I assume you're going to use infinity objectives, the best place for the analyzer is in the infinite space, between the objective and the tube lens.
In microscopes the main advantage of infinite versus finite systems is the ability to place flat optical components like filters, prisms and beamsplitters in that space without altering the tube lenght and minimizing optical aberrations (this kind of systems were usual in metalurgical microscopes well before being implemented in biological ones as standard)

A circular polarizer may be preferable with a DSLR because the camera meter can be fooled with plane polarized light because the main camera mirror is a semitransparent one. To shot in live view or manual mode it will be indiferent.

But be aware that microscope polarizers are designed to work crossed while photographic ones aren't and the extintion may be lower and many of them induce a strong color cast when crossed. If you already have this filter you may test it crossed with the microscope one in front of bright lamp.

Some microscope analyzers are circular ones or linear with a depolarizer in the eyepiece side. This ones have all the advantages.

more discussions about this topic:
http://www.photomacrography.net/forum/viewtopic.php?t=10821&highlight=
http://www.photomacrography.net/forum/viewtopic.php?t=10706&highlight=analyzer+circular+cross
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Pau

[Chris S.]

I've tested an Olympus microscope analyzer, an Edmund Optics Techspec High Extinction linear polarizer, a photographic B&W circular polarizer, and a linear one from Tiffen (an older model, so perhaps not representative of current production). The Olympus analyzer and Edmund polarizer are very close to one another, and much, much better than the two photographic polarizers, for extinction and color neutrality. Hence, I gave up all thought of using photographic polarizers after observing this. I now keep the analyzer in my RMS filter mount, and the Edmund polarizer in my Mitutoyo filter mount. Any difference between the two, if it exists, would be splitting hairs.

In addition to extinction and color, another disadvantage of photographic polarizers, is their mechanics. The rotatable ring assembly is fine when the filter is atached to the front of a camera lens, but is less than ideal for holding a microscope objective steady and without sag. Note that I'm using a horizontal configuration; in a vertical rig, the effect might not be noticed as much.

A nice feature of the Edmunds offerings: they come in wide variety of sizes, so that one can mount them in an appropriate tube and adapt as needed. Though conveniently, my Olympus analyzer happened to be just right to fit into an appropriate tube for use with RMS adapter parts.

BTW, my tests were done with Edmund Techspec polarizing sheets, which have similar specifications to the Edmund Techspec polarizer, to polarize the light source(s).

--Chris

--edited slightly for clarity

[Craig Gerard]

Thanks for the advice.

I have an Olympus microscope analyser. I will fit that into the assembly and apply circular polarisers to the light source when required.

I made some changes to the area where the iris assembly attaches.

The sharing of the internal threads of an M52 to M42 step ring was a potential hazard due to thread depth restrictions.

A second Nikon to M42 adapter has been deployed in its place. Attached to the latter is a Nikon BR3 which terminates in a female 52mm thread. I have screwed the spare M52 to M42 step ring into the thread of the BR3. The iris assembly screws into the step ring and does not need to 'share' the thread as demonstrated in the initial images.

This modification increases the total length of the assembly to 100mm (before displacement of the Unifoc 12) as opposed to the original 85mm.

I'll take an image an upload.

An M42 coupler with internal threads would provide a more streamline solution. Is anyone aware of such an adapter?





Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[SONYNUT]

_________________
..............................................................................
Just shoot it......

[Craig Gerard]

SONYNUT,

The horse comes first, then the cart (or possibly a pile of manure).


Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[SONYNUT]

LOL....YOU NEVER KNOW...
_________________
..............................................................................
Just shoot it......

[SONYNUT]

I know you like to experiment....

http://www.photomacrography.net/forum/viewtopic.php?t=14518&highlight=
_________________
..............................................................................
Just shoot it......

[Craig Gerard]

The Nikon BR3 serves a dual purpose. It permits risk free attachment of the iris assembly via an appropriate step ring and the 52mm female thread also accepts the 52mm threaded microscope objective adapters which were designed to work without the iris assembly.

Olympus polariser (drop in) is inside the assembly.

Initial test images reveal no significant vignetting and good resolution corner to corner on the Canon 50D.

When I find a respectable subject I'll upload some images and a crop; plus an overall image of the setup.

Currently working with the Mitutoyo M Plan Apo 5X.

(the large numbers represent millimeters)





*With the Unifoc 12 positioned between the objective and tube lens there is no increase or decrease in magnification when displaced. It simply serves as a focusing aid.
This is not unexpected because it is located within the 100-200mm 'variable' area (see diagram below) which is one of the attributes of an infinity-corrected microscope.




I'm curious to see what happens when the Unifoc 12 is placed 'behind' the tube lens (*see note below). When displaced, it will effectively increase magnification, to some extent, this may possibly be a more desirable role, due to its precision?

*Later note: (viewfinder observation)

When placed 'behind' the tube lens, maximum displacement of the Unifoc 12 resulted in FOV 4.6mm. Minimum or no displacement of the Unifoc 12 resulted in a FOV 4.8mm.
Conclusion: The Unifoc 12 is used to best advantage as a focusing helical between the objective and the tube lens; but for most purposes it is not required when other means, independant of the lens, are available for course and fine focus.


Nikon PB-4 bellows draw = 52mm (MXA20696 @ infinity). FOV with 5X objective 4.4mm (approximate) @ 52 mm extension. FOV with 10X objective 2.2mm @ 52mm extension. Total distance from tube lens to sensor/image plane =150mm when using a Canon 50D.



Craig

edit: updated/corrected some technical details.
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[Craig Gerard]

Couple of overall setup images. (these were taken with an M42 JML Optical 28/2.8 Macro, Made in Japan?)








Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

[Brodie Foster]

Off topic sorry, but how is that JML 28mm f2.8 macro? I realise it is probably no better than any other 28mm f2.8 macro but the 'JML' part is taunting

[lauriek]

I suspect we've had this conversation in the past but what are those arms your flexible light guides are held in place with - are they 'Noga's?
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Flickr | www.laurieknight.net

[Craig Gerard]