Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

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JCTyler
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Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#1 Post by JCTyler » Mon Sep 12, 2022 8:19 pm

I've narrowed down my choice for a lens to examine minerals with. I'm thinking about getting one of these used. Leitz is another name for Leica so I'm confident about the quality of optics and build with this.

Does anyone have experience or reconmendations with this as a LWD lens to work with?

https://www.ebay.com/itm/174978774736?h ... olid=10049

PeteM
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#2 Post by PeteM » Mon Sep 12, 2022 10:20 pm

That objective is typically used with an inverted microscope, peering through something like a Petri dish, and for phase contrast.

"Scarodactyl" is the resident expert on imaging minerals and gems, but I think he'd recommend something more like a long working distance metallurgical objective. The one you've picked won't really have a lot of working distance to illuminate from the side. It's not meant for epi illumination through the objective, which you may want to do at some point. And the phase ring will likely be a slight decrement in your application.

Can you remind us what microscope you hope to use - that can influence the choice of affordable alternatives.

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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#3 Post by Scarodactyl » Tue Sep 13, 2022 10:39 pm

Leitz isn't really just another name for Leica--Leica is a frankenstein sewn together from several companies, and I don't think that much Leitz actually survives in the final mix.
This objective would not be a good choice for photography for several reasons:
It requires specific eyepieces to give full performance, without them the image will be poor.
Following up on the above even if you get things set up with a correcting eyepiece you'll be limited to something like an 18mm field number, requiring extra magnification to cover a larger sensor.
It is a phase contrast objective and the phase annulus will reduce image quality with no benefit.
The numerical aperture is not very high to start with so you're not going to get great resolution.
The working distance is 6.7mm which is not bad for a 20x but not amazing either.

Yeah, it's fairly cheap, but I don't think you're going to get the results you want with it.

If your focus is photography on three-dimensional opaque subjects then you should be looking for metallurgical objectives that don't require eyepiece corrections. In the finite era that's mostly Nikon CF objectives, and in the infinite era that's Nikon, Olympus, Mitutoyo and many, many Chinese, Indian and Japanese copies of those. Unfortunately these also tend to be priced a bit higher since you're competing with other people who want to use them for this purpose in addition to people wanting them for typical microscopy.
As an example, this is a Nikon BD plan 20x elwd objective: https://www.ebay.com/itm/225159931639
Note the superior resolution with an NA of 0.4. It also has a superior working distance of 8.5mm, and the image can be directly projected onto an aps-c sensor with no intermediate opti s (likely the corners eill not be incredible but nothing like as bad as you'd see with the Leitz if used this way). It is a BD objective, meaning it has an outer shroud allowing light to be fed around the outside of the objective for darkfield imaging, so you'd need to cover the back of that outer channel to avoid light leaking in (and m26 to rms adapter will do this). It's also possible to remove the outer shroud to get some more working distance and make it all skinnier to avoid blocking your illumination, though this would likely require some careful and slightly destructive modification.

JCTyler
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#4 Post by JCTyler » Thu Sep 22, 2022 12:16 am

Thanks for the guidance. I replyed to a seller saying I'm interested in a Nikon BD Plan 20 0.4 210/0 ELWD an he says won't work with my microscope. Its a Russian/Chinese XSC-04. I bought it with the 20x missing. It came with a 10x (7mm WD) and 40x (.5mm WD) As far as I know the Nikon is RMS threaded as is the XSC-04. I measured roughly for the Nikon lens attached with enough distance to examine the sample. Is there something I'm missing here? I can add additonal lighting and unscrew the table if needed to work with and manipulate the sample.

https://www.mrcad.co.uk/?product=russia ... -eyepeices

Scarodactyl
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#5 Post by Scarodactyl » Thu Sep 22, 2022 1:16 am

Ah, for some reason I thought you were assembling more of a photo-focused rig. The Nikon BD plan has a 26mm thread and also expects a 210mm space rather than a normal 160mm. That could be accommodated on this scope by lengthening the eyepiece tube in some way or another, but generally speaking I don't think this style of scope is a good match for photographing minerals. It will likely not allow you to lower the stage enough to image thick specimens and it's generally not a good ergonomic match either. Unless you mean to look at petrographic thin sections, in which case there are other issues that would make it less ideal.

JCTyler
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#6 Post by JCTyler » Sat Sep 24, 2022 1:17 am

If the total length of 210mm is the goal would an adapter of 50mm (say a metal or plastic tube) added to the 10x eyepiece and an RMS to M26 adapter work for the lens? Would the 50mm tube add distortion? Or would just getting a 20x eyepiece be a better idea and work with the 10x?

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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#7 Post by Scarodactyl » Sat Sep 24, 2022 1:27 am

A spacer would be necessary, and would not introduce any distortion. A 20x eyepiece would not help.

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Re: alternative 20X LWD Objective

#8 Post by blekenbleu » Sat Sep 24, 2022 9:15 am

Here is an OLYMPUS LWD CDPlan 20x for 160 tube length that accommodates no cover glass,
but wants a matching eyepiece for corrections
https://www.ebay.com/itm/393988799904

You might want to consider something like this:
https://www.ebay.com/itm/265900186843
It has a vertical illuminator, which is very convenient for viewing opaque objects,
with slots for e.g. polarizing filters, already including an analyzer
and the BD Plan 20X ELWD objective, among others.
Metaphot, Optiphot 1, 66; AO 10, 120, EPIStar, Cycloptic

JCTyler
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#9 Post by JCTyler » Wed Oct 19, 2022 7:36 pm

Are there any quality/fit issues for adapter ring quality on RMS male to M26 female? I'm weary of dealing with Aliexpress and hit and miss quality control in the past. Does anyone know who makes a quality piece?

https://www.ebay.com/itm/384620411818?h ... R47i85n-YA

Scarodactyl
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#10 Post by Scarodactyl » Wed Oct 19, 2022 8:41 pm

Thorlabs has some good adapters that are not insanely expensive (weird for them) and come with snacks.
Chinese adapters are usually OK but I have had mixed results in terms of fine centration.

JCTyler
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Re: Leitz Phaco 1 - Phase Contrast L 20X/0.32 LWD Objective Lens

#11 Post by JCTyler » Sat Feb 11, 2023 12:57 am

Does the RMS to M26 adapter at 5mm to the tube length? Should I have made an adapter of 45mm and not 50 mm? I've just made a temp one for now out of some plastic tubing.

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