Want to learn more about eyepiece

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ker2x
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Want to learn more about eyepiece

#1 Post by ker2x » Fri Mar 04, 2022 1:05 am

Friendly greetings !

So now I have 2 microscopes (+ a cheap binocular) :
- Leitz Dialux from 1953
- Nachet NS400 from 80~90's something (not really sure)

I got both for fairly cheap but dirty/damaged/incomplete.
Anyway, with your help + Facebook + Discord + google. They're both useable and clean enough.

I'm also into photography and video since a long time (I even have a Leica M Monochrom), I'm also self taught in geometric optic and physical optic.
I can't do the math but I know the general principle of both. (even if I'm still confused about a lot of things of course)

Being into photo/video, I somehow focused on the objective and totally forgot about the eyepiece.
I was a bit frustrated about the tiny front lens of the Leitz eyepiece, and the lower FOV, but I didn't really think too much of it.

Yes, it's turning into a long post I suppose.

An acquaintance pushed me to get the Leitz (and I have no regret whatsoever, thank you) and hinted me that it would have excellent quality.
I was a bit disappointed at the quality at first but then I found out that the Leitz was extremely dirty, put a lot of hour into cleaning it. I disassembled and reassembled it completely (except some obvious "do not touch" part with springs are gear ball that wouldn't contribute to optical quality anyway)

Now the Leitz is clean, as clean as the Nachet that I didn't disassemble due to its complexity and my inexperience.

Yet, the Nachet still had a higher image quality overall by a large margin. Of course it have stuff like kohler illumination and 2 diaphragm and stuff that the Leitz don't have, but I knew that wasn't the main problem.

At some point in order to check if I had to clean the 100x objective : I swapped the eyepiece and put the Nachet eyepiece on the Leitz Microscope.
Massive improvement !! wowzer !

I'll say it : the Leitz eyepiece I have s*ck, hard, at least compared to the (much?) more modern Nachet Eyepiece.

Are the Nachet eyepiece really good ? No idea.

But now I want to learn more about eyepiece. I feel so dumb about ignoring it entirely while it's obvious that it's an integral and important chain of the light path.
Simple design, good brand, what could possibly go wrong ? well... something... (very) apparently.

And I don't find much information about it.
I find that there are different type, and they're mostly marketed around confort of use (or specialized eyepiece) but nothing much about quality.
Official brand website are super cryptic about them too.

Do you know good ressources about it you can share ?
I want to replace the Leitz eyepiece by something of better quality and yet still affordable .
I don't even know about a good price range for eyepiece. It goes from $20 to infinity, as usual...

I'm not strictly looking for pure buyer advice but more about the fundamental of when to use what.
They have diameter, magnification, no specific tube length, of fairly simple design.
That's pretty much the limit of my knowledge specific to eyepiece (then various level of aberration correction and different material or coating, just like any other optical elements).
That's all I know about it.

some pics of my 2 microscopes & eypieces, for comparison
Image
Image

Thank you.

BramHuntingNematodes
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Re: Want to learn more about eyepiece

#2 Post by BramHuntingNematodes » Fri Mar 04, 2022 2:43 am

I use a much more recent eyepiece on my Dynoptic than the rest of the scope, but it still has to match.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

ker2x
Posts: 93
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Re: Want to learn more about eyepiece

#3 Post by ker2x » Fri Mar 04, 2022 10:23 am

BramHuntingNematodes wrote:
Fri Mar 04, 2022 2:43 am
I use a much more recent eyepiece on my Dynoptic than the rest of the scope, but it still has to match.
What need to be matched ?

apochronaut
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Re: Want to learn more about eyepiece

#4 Post by apochronaut » Fri Mar 04, 2022 1:05 pm

There was a bit of an optical revolution in the 1950's, when a greater supply of different optical glasses began to be available. This allowed microscope companies to apply more complete correcting of the image over a broader field and put it in a package that was within the budget of the intended market. This progressed even further over the decades until today you can have a well corrected field of view out past your ears : enough so that you have to turn your head in order to see the edges.
Your Nachet was built in a time when infinity correction and a reasonably broad field of view were becoming common and the eyepieces are integrated into the rest of the optics. Eyepieces can provide corrections that span a range from moderate undercorrection through neutral correction to moderate overcorrection. In each optical system, the eyepiece must provide just the right amount of correction in order to have the flat, well corrected field, the engineers intended it to have.
Your Leitz microscope was built about 20 years prior to your Nachet. It has a 170mm tube length and the eyepieces are designed to perform specific tasks to provide ax good an image as possible. The periplan designation implies that they perform part of the job of making the image plan or flat . They also are required to pick the image up 18mm down the tube, which is a focal distance unique to leitz. It was not common for microscopes to have more than an 18mm field of view as well, at the time your Leitz was manufactured but some manufacturers offered eyepieces with an extra wide field as a more expensive option too.

Your enthusiasm for the Nachet eyepieces is mostly due to the fact that they provide a wider field of view but is that extra field well corrected when used on the Leitz? Check that carefully. It isn't impossible for that to be the case but more often than not the level of planar and chromatic aberration corrections is different across manufacturers and even though you get a wider field, the field may have curvature and or coloured banding as you look towards the periphery.

viktor j nilsson
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Re: Want to learn more about eyepiece

#5 Post by viktor j nilsson » Fri Mar 04, 2022 3:14 pm

I've always been a bit confused by the many different varieties of Leitz eyepieces. But based on this discussion:
viewtopic.php?t=13733
I believe that it is a general rule that eyepieces made for 170mm Leitz microsopes does not have a field number written on them, while eyepieces made for 160mm microscopes typically do.

So if you want a wide field (GF) periplan eyepiece made for a 170mm microscope, I believe that this is what it should look like:
https://www.ebay.com/itm/373763381173

Please correct me if I'm wrong!

ker2x
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Re: Want to learn more about eyepiece

#6 Post by ker2x » Fri Mar 04, 2022 3:15 pm

apochronaut wrote:
Fri Mar 04, 2022 1:05 pm
Your enthusiasm for the Nachet eyepieces is mostly due to the fact that they provide a wider field of view
Ho yes. probably. certainly.
apochronaut wrote:
Fri Mar 04, 2022 1:05 pm
They also are required to pick the image up 18mm down the tube, which is a focal distance unique to leitz.
I don't understand :(


Other than the FOV, I enjoy the higher contrast. But I was told that it may (possibly) come at the cost of resolution. (that confuse me but ok?)

I'll try a much more qualitative comparaison.
I also ordered (I receive them next week) a pair of noname $10 WF10X 18mm eyepiece just so I can compare Leitz vs Nachet vs Aliexpress :mrgreen:

When you're talking about planar aberration correction I assume you're talking about spherical aberration ?
I'm not really noticing any.

About chromatic aberration. With the Nachet eyepiece on the Leitz microscope I have a very obvious orange fringe at the very border of the view.

EDIT : pics removed. They're both blurry.

viktor j nilsson
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Re: Want to learn more about eyepiece

#7 Post by viktor j nilsson » Fri Mar 04, 2022 3:32 pm

ker2x wrote:
apochronaut wrote:
Fri Mar 04, 2022 1:05 pm
They also are required to pick the image up 18mm down the tube, which is a focal distance unique to leitz.
I don't understand :(
Image

This image, which is found in one of the links in the thread I linked to above illustrates the issue. Leitz 170mm microsopes have a long tube (170mm), and the eyepieces are designed to pick up the image very far down this tube (18mm from the top). When you are using an eyepiece designed for a 160mm eyepiece on a 170mm scope with 170mm objectives, the eyepieces are not focused at the height where the image should be (18mm down the tube), they are focusing 10mm down the tube. You will get an image, but in order to create an image here, 10mm down the tube, you need to re-focus by moving the objective. This means that the objective suddenly is not operating the way it should. In some cases this introduces relatively mild aberrations, but in some cases the aberrations are severe.

apochronaut
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Re: Want to learn more about eyepiece

#8 Post by apochronaut » Fri Mar 04, 2022 3:37 pm

It is hard to notice spherical aberration. It exists as varying degrees of an out of focus or clouded image. Your pictures don't really show anything because your sample is too small, since all eyepieces are fairly equivalent on axis or fairly close to the axis. It you have a better subject with higher contrast , something with highly defined borders on a white background and have the subject large enough to cover over to the perimeter of the Nachet eyepiece, you will likely see some chromatic aberration and possibly lack of planarity when used with the Leitz objectives. Planar correction is that which corrects the image to correct for curvature of field. All microscope objectives theoretically will have curvature of field. This can be corrected for in all locations of the optical system but in an infinity corrected system it often happens in the telan lens and or the eyepiece as well as partially in the objective. The planar correction is unlikely to be the same in the two eyepieces.
The orange ring at the field stop of the Nachet eyepiece indicates that it is a compensating type. The blue border at the field stop of the Leitz eyepiece indicates that it a correcting type. They are on opposite sides of neutral.

The reference to the Leitz eyepiece picking the image up at 18mm is the focal length of the eyepiece. The Leitz periplan eyepieces from that era had an unusually long focal length. With most eyepieces it is somewhere around 10mm.. This can affect corrections and the magnification. Sometimes accidentally, a lack of correction can be cancelled out somewhat by the difference in focal length too but the magnification will be affected. The Nachet eyepiece used in the Leitz microscope will provide a lower magnification than the Leitz eyepiece: probably about 5% lower, which will make the field seem larger than it actually is.

ker2x
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Re: Want to learn more about eyepiece

#9 Post by ker2x » Fri Mar 04, 2022 3:52 pm

Thank you for the clear explanation !

ker2x
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Re: Want to learn more about eyepiece

#10 Post by ker2x » Tue Feb 07, 2023 11:25 pm

a small update about the "low quality" of the Leitz.

When i cleaned up the Leitz, i forgot to clean one of the internal lens of the microscope.

Yes, it's supposed to be fully transparent :
Image

Scarodactyl
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Re: Want to learn more about eyepiece

#11 Post by Scarodactyl » Tue Feb 07, 2023 11:51 pm

That'll do it! Plus side it looks like mold didn't set in which is great.

apochronaut
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Re: Want to learn more about eyepiece

#12 Post by apochronaut » Wed Feb 08, 2023 5:16 am

After almost 60 yesrs of looking through microscopes, I am still flabbergasted as to how all that stuff gets in there?

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