190 mm tube length objectives on a 160 mm tube length instrument?

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georgetmacro
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190 mm tube length objectives on a 160 mm tube length instrument?

#1 Post by georgetmacro » Mon Sep 18, 2017 10:48 pm

This image take through Carl Zeiss APO 11X 190 mm tube length (eyepiece 10X) on a Nikon S 160 mm TL. The image is the result of 57 stacked images
This image take through Carl Zeiss APO 11X 190 mm tube length (eyepiece 10X) on a Nikon S 160 mm TL. The image is the result of 57 stacked images
BlackAntFootWeb.jpg (187.5 KiB) Viewed 7595 times
Hi everybody.
I am new to this forum so will tell all a little about myself. I am not completely new to microscopy as I have a Bachelor of science B.Sc., Biology/Human nutrition degree from Wollongong uni, NSW Australia ... a Post graduate diploma PGradDip., archaeology/paleoanthropology from Armidale uni NSW Australia and am currently studying towards my Master's degree., archaeology at Armidale NSW Australia.
I am 69 years of age. I have a few microscopes both biological and stereo dissecting, (Nikon S series, Lomo Biolam and a Olympus stereo dissecting). My first forum question is this.
I have a set of 4 Carl Zeiss Jena APO objectives (11X, 22X, 40X & 94X) in 190 mm tube length ... if I want to use them on a 160 mm instrument, what should I do? I have already photographed using the 11X fitted to the Nikon S and the result appears better than that of the Nikon 10X standard objective (57 images stacked).

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zzffnn
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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#2 Post by zzffnn » Mon Sep 18, 2017 11:32 pm

Welcome to the forum.

Do your 190 tube length objectives say "ncg" or no cover glass on them? What are their respective NA (numeric aperture values)?

Most likely, your 11x objective has low NA and does not require adaptation to use on 160 mm tube length. 40x and 94x would need 30mm extension. 22x would depend on your exact NA.

Nikon S may not be extended to 190mm easily. LOMO Biolam can, but needs LOMO's epi illuminator attachment, I think (LOMO offered 190mm tube objectives for Biolam), but Biolam's fine focus may not travel long enough for stacking?

Usually, an extension part of 30mm or 50mm is added to the space between scope arm and head. That attachment is usually brand/model specific though.

apochronaut
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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#3 Post by apochronaut » Tue Sep 19, 2017 1:32 am

The intermediate image distance for a 160mm instrument is 150mm. That means that the objective provides a fully corrected intermediate image equivalent to the marked magnification at 150mm distance from the shoulder of the objective.

Objectives corrected for 190mm would provide a corrected intermediate image at somewhere around 180mm. The 30mm difference means that there will be a roughly 16% lower magnification for each 190mm tube length objective and there will be some spherical aberration, moreso with low magnification objectives, than with higher ones, although the differential here is quite large and spherical aberration will likely occur with all objectives.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#4 Post by georgetmacro » Tue Sep 19, 2017 4:47 am

Thanks heaps for that information.
The objectives do not show a NCG on them but the NA is written on them as follows.
11X NA = 0.35
22X NA = 0.65
40X NA = 0.95
94X NA = 1.40
Based on the responses does it mean I can add 30 mm to the tube length between the top of the tube and the euepiece?
What about, as an alternative, adding an extension to the actual objective ... I have ordered some is it, RMS extensions on EBAY. They are 7 mm long and I have ordered 4 of them to see if that is a possible option. An idea I have for the Lomo is to put a spacer between the base mounting plate and the microscope then remove the stop pins to give the microscope more travel. I used to run my own business 'Classic Photo Optics' servicing and repairing mechanical cameras, lenses etc so can do the modifications myself in a way that they can be reversed if necessary. I will also contact a chap in russia that I am dealing with re the special attachment availability. I have attached a picture of the Carl Zeiss Jena APO objectives. Thanks again for the suggestions and interesting conversation. Cheers George.
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Image of the Carl Zeiss Jenna 190 mm tube-length objectives I am experimenting with.
Image of the Carl Zeiss Jenna 190 mm tube-length objectives I am experimenting with.
AllThe AZ APO lensesAt190TL 2.jpg (198.27 KiB) Viewed 7577 times

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#5 Post by zzffnn » Tue Sep 19, 2017 11:58 am

There are 10mm objective extensions on eBay. But they are awkward to use. You may not be able to rotate your objective turret after adding more than 2 sets of 30mm's.

It may be cheap to just buy a LOMO epi light attachment too. To use 22x and above (which all have very short working distance), you need that epi illuminator attachment anyway.

Your 22x has high NA and requires 190mm tube. It won't work well on 160mm tube.

LOMO made some 190mm low NA achromat (not high NA apo) objectives and I think they are NCG type. You can ask you Russian friend to confirm.

I also suggest:
1) search for old catalog information for those objectives:
2) if you cannot find it, then join photomacrography.net . There is at least one member there who knows Zeiss Jena and LOMO very well.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#6 Post by apochronaut » Tue Sep 19, 2017 2:05 pm

It looks like you have objectives from two different series here. The 11x .30 is designed for a shorter tube length and due to it's N.A. is relatively cover glass neutral. It's performance will not be that affected by whether it is used with or without a cover glass. I don't see any reason why it will not work well on your Nikon and due to it's apochromat design, provide improved performance.

The other 3 are a whole other story. They are what are called " short mount objectives". The actual lens pack of each is very similar to the lens pack of a longer body objective, with slight differences for the cover glass correction, but the hollow objective body of predictable length, is missing. In the application your objectives were designed for, it is replaced by the body of a vertical illuminator, located between the bottom of the ocular tube and the objective. This is why the tube length is engineered to be so much longer, because the vertical illuminator housing eats up a certain amount of space, and 190mm was as short a tube as they could conceivably make. There was also a sort of convention associated with the design of older vertically illuminated microscopes, in that objectives from other mfg. could be used on various stands. 190mm was a common tube length.
They are metallurgical objectives, designed for the visual assessment of polished metallurgical samples, without a cover glass.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#7 Post by georgetmacro » Tue Sep 19, 2017 8:56 pm

Thanks for all of the very useful information ... I will persevere with these and other objectives given what you guys have enlightened me with. I have a couple of Lomo APO's (160 mm tube length) on the way to me from Russia that I am looking forward to trying out. Many years ago while studying towards my first degree in biology I used my Lomo Biolam with the standard objectives that came with it ... I even published my final work including the images from the oil-immersion objective ... a bit ordinary given my experience and limited knowledge but it definitely did the job ok photgraphing (film of course) pollen grains. If anybody is interested go to (http://publications.rzsnsw.org.au/doi/p ... =rzsw-site)
Cheers George

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#8 Post by apochronaut » Wed Sep 20, 2017 11:51 am

You will probably find that you need Lomo or Zeiss Jena compensating eyepieces for those Lomo apochromats. Designers, for many years were handcuffed by the glass formulas available to therm and could not produce an apochromat with complete correction of both chromatic and spherical aberration at the same time. Probably it was possible in a larger barrel and at great cost but the cost effective solution was to apply a combination of overcorrectton and undercorrection in the objective/eyepiece combination, in order to achieve excellent correction of both chromatic and spherical aberration.

With older apochromats you will get adverse chromatic aberration when using most eyepieces not designed for the specific combination but accidents can happen. I came across a no-name 5x eyepiece that looks like it is huygens and it is better corrected for Spencer apochromats than the Spencer 5x compens.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#9 Post by apatientspider » Thu Sep 21, 2017 4:02 pm

apochronaut wrote:You will probably find that you need Lomo or Zeiss Jena compensating eyepieces for those Lomo apochromats.........

With older apochromats you will get adverse chromatic aberration when using most eyepieces not designed for the specific combination but accidents can happen. I came across a no-name 5x eyepiece that looks like it is huygens and it is better corrected for Spencer apochromats than the Spencer 5x compens.


Phil,

Not to hijack the thread, but if one is in-experienced with compensating eyepieces and apochromat objectives, how does one tell? I mean, specifically what does the chromatic aberration look like? Or does that vary by particular brand?

For example: I received some eyepieces marked Carl Zeiss, C 10x, Germany in an odd lot of lenses not too long ago. I assume the "C" stands for compensating, but how can I tell for certain? If they are compensating eyepieces, what should I get when using them with a different brand of apo objective, like a Spencer? What would I get using them with ordinary achromats?

Jim

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#10 Post by apochronaut » Thu Sep 21, 2017 5:37 pm

American and British eyepieces( Spencer, AO, B & L, Baker, Cooke-Baker, CTS, Vickers, Beck, Watson) have comp. or compens stamped , usually on the top of the eyelens perimeter.

German and Austrian eyepieces are stamped k, kompensating or komp, with a k. being used instead of a c. Japanese followed the English spelling mostly but I am not sure what took place with early Japanese eyepieces; ww. II to 1960 or so. The early Japanese optical industry was heavily informed by German concerns, later , after the event of Occupied Japan, and the opening of U.S. markets to cheap Japanese products, they started to copy U.S. patterns.

Compensating eyepieces are almost always marked in my experience but I have encountered some very old ones, that perform like compensating eyepieces but are not marked as such


these are not to be confused with plan kompensating eyepieces which are designed to complete the plan correction of the objective.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#11 Post by zzffnn » Thu Sep 21, 2017 7:27 pm

Jim,

I heard CA of uncompensated apo objectives do vary by brand/product lines.

What you would get is hard to say. You may find "mismatched" EP-obj pair actually image pretty well. Low magnification/NA is usually more forgiving than higher ones.

If you stare into edges/shadows of thick/transparent/low contrast subjects, you may see CA more clearly in some extreme settings. CA usually show up as purple, blue, yellow colors make edge lines fuzzy.

If you are a wide man like me, who likes to pushes optics into unfavorable conditions (e.g., using extreme oblique or darkfield illumination on thick/transparent/optically active subjects such as a thick diatom), you would see CA easily. Otherwise (when viewing high contrast flat subjects under plain brightfield or low magnification reflected light), you may not see it (I cannot see it in many of those favorable conditions).

Also, well-compensated apos should produce more defined edge lines for subjects. And it is also more obvious in DIY oblique or darkfield.

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#12 Post by apatientspider » Thu Sep 21, 2017 7:55 pm

Fan,

Thanks to both you and Phil - your answers help considerably.

I have a full complement of AO/Spencer compens eyepieces for my Spencer research #5 now, so I should probably just take the time to gather everything together and do some further comparing. But now I'll know better what to look for.

Jim

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Re: 190 mm tube length objectives on a 160 mm tube length instrument?

#13 Post by apochronaut » Fri Sep 22, 2017 5:15 pm

I have not found that the elevation of the N.A. has much to do with enhancing the ca, when matching apochromats and compens eyepieces but I have found that lower eyepiece magnifications, tend to enhance it i.e. the same sample imaged with a specific objective and a 10x compens, can have less ca, than the same sample imaged with the compatible 5x compens.

With older apochromats, the math was there but the glass to prove the math in practice, and the ray tracing imaging required to show where the design was diverging from the math, due to diffraction, and flare due to unwanted reflection, wasn't there. No doubt, empirical evidence proved very important in refining the ultimate production model and while most were pretty close, some were better than others and the compensation levels required based on one manufacturers ultimate design would diverge somewhat from another's.

Spencer and AO for instance, despite the fact that there was considerable movement of employees between those two northwestern N.Y. state giants, produced apochromats with decidedly different characteristics and the compens eyepices of one are ill matched to the other.

With older apos, there still is some ca but it is much reduced , when compared to achros from the same factory and oddly, the diffraction of achromats, can produce a false contrast, rendering hard dark edges around objects, which gives the illusion of contrast, whereas an apo renders a thin accurate line, giving a sense of less contrast,

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