Nikon Projection Lens - CF PL

[Sunrune]

Just wondering what the difference is between a (finite) Nikon CF PL 2.5X and a CF PL 2.5XA. What is the 'A'?

Thanks in advance.

[gekko]

Sunrune, I'm not sure, but I have a vague recollection that the X indicates that the lens can be used with an eyepiece reticle. I hope someone who knows for sure will reply.

[Sunrune]

Thanks Gekko.

A good search around the web didn't unearth what the 'A' means. But, based on the theory that if the two weren't interchangeable I would have heard about it, I have a CF PL 2.5XA on the way

[microcosmos]

I'm posting in this thread after 5 years in the hope that someone now knows the answer to the original question - what is the difference between Nikon CF PL 2.5X and Nikon CF PL 2.5XA? I've been unable to find any information so far.

I'm asking because I'm considering using the CF PL2.5x on my Olympus BH2 trinocular head instead of the NFK2.5x (I'm not yet sure about its parfocality etc). The microscope has been converted to infinity and the objectives I'm using are already fully corrected, and the NFK gives ghastly aberrations.

[Scarodactyl]

In my testing the xa had fewer aberrations. I think it was sold on particular with the smz-u/10a so later on. I don't like the normal pl 2.5x that much, it adds too much ca of its own. It kinda makes sense, that design must date back to the 70s with the first cf optics.
You might want to try the cfi 2.5x as well. Not a very scientific test, but I tried both a cf pl 2.5x and a cfi 2x on my smz1500 and the pl 2.5x gave bad ca in thr corners on aps-c as usual but the pli was dead clean corner to corner.

[microcosmos]

Thanks, that helps a lot. I didn't realize the PLI was actually the CFI version as it didn't have "CF" in the designation. I can only afford one so I'll probably go for the PLI.

By the way I just noticed by comparing images online that the PL2.5XA has an inner screw thread that goes closer to the top of the eyepiece than the PL2.5X. Perhaps they took the chance to extend the screw thread to make it more parfocalizable to different tubes while they were improving the CAs.

[microcosmos]

Apologies, I got too excited. Just realized after making measurements that the upper part of the PLI and PL is too wide to fit in the standard Olympus BH2 photomicro adapter tube.

As I have a third-party version of the adapter that is modular, I could look for appropriate step-up and step-down rings to take a wider tube that accommodates the PLI. I'll have to look into this.

[Scarodactyl]

Just as another question, which objectives and what format camera?
I have used a pl 2.5x on an olynpus scope (szh) and where it sat in the tube got ok results (though my testing ability was very limited at the time). Pli eyepieces come in both 30mm and 23mm so you'd need the 23mm for sure.

[microcosmos]

Hmm interesting, I saw some PLI's on ebay that seem to have a removable (appears to be a set screw at the side) 30mm sleeve over a 23 mm tube that slightly protrudes from the sleeve.

I'm using Olympus UIS fluorite objectives, which produce a fully corrected image. The Olympus PE photo eyepieces made for these objectives don't fit on the BH2 head - they're 24+mm.

(There's a complicated story as to why I have to use these objectives in my particular setup, instead of the BH2-era objectives which would work fine with the NFK.)

The camera has a 35mm-format full-frame sensor.

[MichaelG.]

I'm using Olympus UIS fluorite objectives, which produce a fully corrected image. The Olympus PE photo eyepieces made for these objectives don't fit on the BH2 head - they're 24+mm.

Yes, they did that to prevent people inadvertently using the wrong photo-eyepiece

But you have created a ‘special’ … so I guess you need to find alternative optics, or modify the BH2 head.

MichaelG.

[microcosmos]

I'm using Olympus UIS fluorite objectives, which produce a fully corrected image. The Olympus PE photo eyepieces made for these objectives don't fit on the BH2 head - they're 24+mm.

Yes, they did that to prevent people inadvertently using the wrong photo-eyepiece

MichaelG.

I can understand the rationale of preventing people who don't really know what they are doing from using the wrong eyepiece, and there might be optical and commercial reasons as well. In fact, I suspect optics are part of the reason, as a larger diameter lens will be less distorted and allow more light through etc. How much of a difference 2 mm makes (23.2 vs 24.8 mm) I'm not sure.

However, if I may be allowed to go off on a slight tangent, I think standardization has more benefits.

Like a large software programme, a microscope system is most powerful and flexible when its components are modular and have backward compatibility so different parts can be swapped out or updated independently according to diverse needs. Olympus and others have mostly followed that strategy - most of their objectives past and present are RMS, and their observation eyepiece tubes are all either 23 mm or 30 mm.

There might be situations (uncommon I agree) where I need to use BH2-era objectives on a BX microscope because the available BX objectives can't handle the particular sample or observation method I need. Then I'd need to stick an NFK tube into the BX. Or vice versa, as in my case, needing to use UIS objectives on a BH2 and not being able to simply pop in the PE photo eyepiece. And I can't just pop in the Nikon either.

I just don't think the manufacturer has to "protect" the customer so much from using the wrong photo eyepiece. The rest of their microscopes already allow so many things to go wrong optically. People can freely use the wrong eyepieces with the wrong objectives, or even the wrong tube length objectives altogether!

It is interesting that objective thread and eyepiece tubes have RMS and universal standards but not photo eyepieces.

I think it's fun to do one's own modifications but some may want to simply get the system working so they can proceed with observations.

I'll see what I can do about this.

[microcosmos]

After further investigation, I have decided that it's easier and optically less risky to try to modify the BH2 head to take an Olympus PE photo eyepiece, than to try to modify it to take a Nikon. I will continue the discussion in the thread on attaching camera to BH2.

Thank you very much for offering your comments and suggestions to help me find the best way forward.

[fero]

In my testing the xa had fewer aberrations. I think it was sold on particular with the smz-u/10a so later on. I don't like the normal pl 2.5x that much, it adds too much ca of its own. It kinda makes sense, that design must date back to the 70s with the first cf optics.
You might want to try the cfi 2.5x as well. Not a very scientific test, but I tried both a cf pl 2.5x and a cfi 2x on my smz1500 and the pl 2.5x gave bad ca in thr corners on aps-c as usual but the pli was dead clean corner to corner.

just for info, I also tried projection lenses but best is direct projection on SMZ1500. In my setup it covers APS-C sensor fully.