Leitz NPL Fluotar DF infinity

[Rorschach]

I have a couple of these and tried to find information by searching the forum but to no avail. Nobody seems to have these darkfield versions, which is a bit surprising.

Being infinity lenses and obviously for epi illumination, they should work perfectly with my Orthoplan/Metalloplan 0.8x/infinity nosepiece, right?

[PeteM]

I have a set of those Leitz BF/Df Fluotar objectives on a Leitz Laborlux 12 HL. This has an epi head fitted to the top and they work fine. I've seen both .8x and 1x heads - recollection is they usually have an infinity symbol marked somewhere on the head.

Might add a photo of your setup, but if you have an infinity Epi head for -- it should work fine. Some of the heads may only be for epi and not have the darkfield illumination option; but that should be pretty easy to check.

[Rorschach]

Thanks Pete, sounds promising! I'll take some photos of the nosepiece and lenses tomorrow. I am missing a few more parts from my Orthoplan system so a direct check is not possible quite yet.

How have you liked the quality of the NPL Fluotar DF lenses in comparison to other high-end lenses?

Edit: one of them is exactly this model: https://www.ebay.com/itm/Leitz-Wetzlar- ... SwORxb9Wml

[PeteM]

. . .
How have you liked the quality of the NPL Fluotar DF lenses in comparison to other high-end lenses?

Edit: one of them is exactly this model: https://www.ebay.com/itm/Leitz-Wetzlar- ... SwORxb9Wml

I'd say they are very good, but not great. These were among Leitz' first infinity objectives; maybe just a bit before the time Olympus did its Neo Splan BF/DF objectives. The Olympus infinity design back then required some corrections in the eyepiece and I'm pretty sure the Leitz do as well. The Leitz try to get the DF annulus within an RMS-sized aperture. The Olympus open it up to 26mm.

My casual impression is that Olympus may be a bit better in darkfield, but I haven't tried a comparison. I am surprised how well some of the old Leitz Neofluar infinity hold up (brightield versions) on a modern Leica infinity scope. The latest Leica infinity have excellent contrast to my eye; likely due to more modern lens coating technology. But take care to avoid stray reflections and Leitz Neofluars are very good.

[Rorschach]

Pete, here are finally the photos of the nosepiece I have. Sorry for the delay!

What can be gleaned from them regarding the darkfield and other usage possibilities?

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[Rorschach]

What to do to check for darkfield capability? Anyone?

[PeteM]

For epi (reflected) illumination, darkfield requires an epi lightpath outside the objective. The Leitz of the BF/DF epi type were flared in shape. If you look at one end on, you'll see an objective on the inside and a light path on the outside sort of like a double-walled chimney pipe with optics in the inner one. These require a head that will fill that outer pipe with light, then bring the image back through the center.

That isn't the type you have. They do provide good images, though, for what they are.

What you could do is use a normal darkfield condenser or darkfield stop in a condenser with these for transmitted light. Recognize that these are zero cover objectives. They'll likely work OK with normal slides up to 10x, maybe 20x. After that you should forego the coverslip and use smears.

[Rorschach]

Thanks Pete, that was super-informative! A bummer about the lack of DF capability as I do not have a darkfield condenser either. But I will have to keep searching for both a DF condenser and DF turret/illuminator.

Regarding the Orthoplan DF turrets/illuminators I seem to have read that there are two different ones: one for RMS objectives and another for larger thread, either 30mm or 32mm.

Seems to be impossible to find any comprehensive list, literature or brochure on the various nosepieces. Apparently there were many! Leitz seems to have been a veritable cornucopia for diversity of microscope components and combinations. But strange that not even a brochure on the nosepieces can be found. I am sure huge numbers were printed.