4x or 5x for a Leitz Dialux 20 EB

[Norbert]

Hi everyone!

This is my first post. I've been nosing about on the forum for a little while now. Since one month I own a Leitz Dialux 20 EB (see photos). It's 41 years old, but works like a charm. I only read histopathology slides on it.
It came with the following Leitz objectives:
- 2.5x PL
- 10x NPL Fluotar
- 25x NPL Fluotar
- 40x NPL Fluotar
- 100x oil

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Going from 2.5x to 10x is sometimes a rather large step when evaluating tissues, so I looked for a 4x or 5x objective online. Today, the mailman brought me a Leitz NPL 5x/0,09 objective, which is truly in an impeccable state. Unfortunately I did not take into consideration that my scope has a tube length of 160mm and the objective is Infinity corrected

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I've looked online for a objective that would fit my microscope, but I'm quite limited in options. I would like to have a 4x or 5x NPL Fluotar objective to fit nicely with the objectives I already have, but as it seems to me there is only the Leitz EF 4x 160/- on the market. Is this the case or are there alternatives? If the EF is my only option, would it give a similar optical quality as my other objectives? The field number of my eyepieces are 18mm, so I guess EF would theoretically give me a flat-focus view, right?

Thanks in advance for your replies!

[Charles]

There is this 4X Plan:
https://www.ebay.com/itm/Leitz-Plan-4X- ... SwpINZZPDr

[einman]

The plan 4x has a flat FOV for up to a 28 mm view compared to the NPL ( Normal Plan) which is flat up to 20mm FOV. The NPL is the cheaper version. EF stood for extended field or what could be termed as achromats.

The Fluotar refers to the degree of chromatic correction. So you have objectives that are flat across a 20mm FOV and are corrected :

" for red and blue light. In addition, the fluorites are also corrected spherically for two or three colors instead of a single color, as are achromats. The superior correction of fluorite objectives compared to achromats enables these objectives to be made with a higher numerical aperture, resulting in brighter images. Fluorite objectives also have better resolving power than achromats and provide a higher degree of contrast, making them better suited than achromats for color photomicrography in white light." - Per https://www.microscopyu.com/microscopy- ... objectives

[einman]

I have this same stand. It is quite good and built like a tank. EF objectives generally work as well as the PLan objectives provided you are not making observations/photos out to the edge of the FOV.

If interested in purchasing a Universal condenser for this scope let me know I have an extra one equipped with one phase-contrast annulus.

[Norbert]

Hi Charles and einman,

Thank you for your quick replies!

The 4x Plan that Charles suggested would be a good option, but then I'm paying for a very wide-view lens of which I'll only be using a small part of its capacity.
At the moment I'm not taking photos, but I might in the future. So a Fluotar might be the best option to benefit from the superior image quality of a fluorite objective when taking pictures.

That leaves me to think that my 'ideal objective' would be a Leitz 4x NPL Fluotar 160. But has Leitz ever made such objectives? I can't seem to find one when looking online.

Thanks again!

[einman]

No I am not aware of one and a quick search gave no indication one ever existed.

[Norbert]

OK, thanks for looking. I'll check if my wallet can support a Plan-objective . If not, I'll settle for an EF one.

Thanks for offering a universal condensor, but this one suits me fine. I'm only doing bright field microscopy and I don't mind flipping the top lens every now and then.

[Micro-Bob]

There is a 6,3 NPL Fluotar too.
With Leitz it is a bit difficult with the fields of planar view. Over the decades there were Pl, PLAN, PL, NPL, PL APO, PL FLUOTAR... and they are all different, logically named only in comparison to their contemporarys.

Holger Adelmann wrote once in german mikroskopie-forum:
"Optik für 160 mm Tubuslänge:
EF "ebenes Feld" bis SZ 18
Plan bis SZ 20
NPL Fluotar bis SZ 22
PL Fluotar bis SZ 24
PL Apo bis SZ 28
(diese Sehfeldzahlen hat Leitz quasi garantiert, wie aber schon richtig angemerkt wurde ist die praktisch nutzbare SZ idR deutlich höher.
Man erkennt auch, dass Leitz den chromatisch höher korrigierten Objektiven auch gleich eine bessere Feldebnung spendiert hat.
Ach ja:
170er TL
NPL bis SZ 18 garantiert
Pl (fürs Orthoplan) SZ 28"

I think there was a first Pl objective series with smaller planar fields.
A EF 4 doesn't cost much money and is easy to find - you might just try if it offers all you need.

[einman]

It can be confusing. When quoting FOV Leitz often included certain assumptions such as your eyepiece and head as well as the turret magnification. Often assuming a 0.8x turret which would automatically increase the FOV as would a larger field eyepiece. Thus my reason for saying "up to" 20 mm and "up to" 28 mm.

[Norbert]

Thanks for all your replies and the comprehensive explanations!

One last question: I saw that the Leitz 4x EF has an numerical aperture of 0.12. The Leitz 4x Plan has a numerical aperture of 0.10. That surprises me as you would assume that the more expensive and higher quality Plan lens would have a higher numerical aperture as its smaller and cheaper EF-brother. Could somebody explain me this seemingly contradictory difference? Is it due to the difference in FOV?