Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

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Seta
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Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#1 Post by Seta » Mon Mar 22, 2021 4:42 pm

Hi,

Finally I managed to get my Olympus BHT almost parfocal with Nikon CFNs (11mm phototube, still 1mm off) but I would like to crop the extreme corners on APS-C; I am managing 4 options:

- Olympus 1.25x intermediate tube. As Olympus scopes are meant to use NFK projection eyepieces I do not know how corner performance will be, maybe is just the center which is good.

- Nikon CF PL2X, to much magnification maybe. They are not cheap but do not cost as much as the Olympus NFK 1.67x either

- Afocal method, tried it yesterday with the eyepiece from a Nikon SC (10/18?) and is not bad; with a 40mm 1.8 konica pancake I get 1.65X; would more modern nikon WF 10/20 eyepieces perform better? any other neutral eyepieces I could try?

- A teleconverter; I have and old 1.5X vivitar F mount and a 2x M42 but for them to work properly they should go inside the trinocular tube, because Nikon/M42 flange distance is larger compared to sony nex (46,5 vs 18mm) Even removing the custom 11mm phototube would not be enough.
Only native sony teleconverter is FE 1.4X TC which is 500$ plus

Has anyone compared these different methods?
Last edited by Seta on Tue Mar 23, 2021 11:37 pm, edited 3 times in total.

Scarodactyl
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs?

#2 Post by Scarodactyl » Mon Mar 22, 2021 8:12 pm

I have a post over here about a few methods I tried.
https://www.microbehunter.com/microscop ... =9&t=10883
Some Nikon objectives will cover aps-c just fine, but if you don't need that level of coverage afocal with a generic 10x/22 or an 8x/10x pl photo eyepiece would be my pick. A good teleconverter would probably be close to ideal but I have not tried that method.

Seta
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs?

#3 Post by Seta » Tue Mar 23, 2021 10:54 am

Scarodactyl wrote:
Mon Mar 22, 2021 8:12 pm
I have a post over here about a few methods I tried.
https://www.microbehunter.com/microscop ... =9&t=10883
Some Nikon objectives will cover aps-c just fine, but if you don't need that level of coverage afocal with a generic 10x/22 or an 8x/10x pl photo eyepiece would be my pick. A good teleconverter would probably be close to ideal but I have not tried that method.
Thanks, I have tried the WF 10/22 against the nikon 10/18? and I would say the nikon performs better (just quick one shot tests) Besides the nikon SC eyepiece is way easier to adapt it has M25 thread so I can put a M42 to M25 adapter inside a M42 tube and the thing is properly held in place.

I am not very good at mounting specimens yet, I may run some tests with the nikon BD plans adding 50mm extension so that coverslip is not taken into

One problem I am having is my old konica 40/1.8 pancake lens exhibits middle hot spot depending on the conditions; most old vintage lenses share this problem.
Maybe I should get a modern pancake designed for modern digital cameras.
Last edited by Seta on Tue Mar 23, 2021 5:26 pm, edited 1 time in total.

Seta
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs?

#4 Post by Seta » Tue Mar 23, 2021 4:44 pm

I just run a test, CFN 10/0.30 via direct projection vs OEM 10/22 Afocal vs Nikon SC Afocal vs Nikon SC as a 1.7X Photo eyepiece-.
The lens used for the afocal tests is a Konica Hexanon 40/1.8 but I keep getting a hot spot in the middle; the eye piece as a Photo eyepiece performs better than expected.

Subject is a printed piece of papper, no coverslip but for a 10/0.30 it does not matter much.

First the Direct projection shot showing the other shots and the 100% crops.

Image

I also made a version of the SC as photo eyepiece with CA correction ticked in CR; 150x150 px crops have global levels adjusted and very subtle sharpening applied

The afocal method center crops show the effect of the hot spot, the SC as a photo eyepiece performs pretty well, the OEM afocal would be the worst

Image

Full size images for anyone to download

Direct projection, OEM 10/22 Afocal, Nikon SC eyepiece Afocal, Nikon SC Eyepiece as photo eyepiece, Nikon SC Eyepiece as photoeyepiece CAs fixed photoshop

I would like to try a modern 40mm for a focal method, like the Canon 40/2.8, until then I think I will use the Nikon SC eyepiece as a Photo eyepiece and see.

Direct projection is still the preferred option, I would like to try a modern 40mm for a focal method, like the Canon 40/2.8.
For now I will use the Nikon SC eyepiece as a Photo eyepiece for small subjects if I want to fill up the frame

viktor j nilsson
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#5 Post by viktor j nilsson » Wed Mar 24, 2021 10:20 am

When you say that you use the Nikon SC eyepiece as a Photo eyepiece, do you mean that you raise it up? How much? Pretty good results with that eyepiece. A bit surprising since the SC system is a basic student-grade microscope that's not really meant to be compatible with anything else. Cool result! Can you show the setup?

Seta
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#6 Post by Seta » Wed Mar 24, 2021 11:09 am

viktor j nilsson wrote:
Wed Mar 24, 2021 10:20 am
When you say that you use the Nikon SC eyepiece as a Photo eyepiece, do you mean that you raise it up? How much? Pretty good results with that eyepiece. A bit surprising since the SC system is a basic student-grade microscope that's not really meant to be compatible with anything else. Cool result! Can you show the setup?
Hi Viktor,

The Nikon SC has some kind of corrective lens after the objectives (pre infinity era prototype?? :mrgreen: ), so I figured out the eyepiece would be quite neutral

Image


Here are the pictures of the different setups.

Direct projection; m37 to m58 step up ring, thin 58mm polarizer glass removed and Nex-58mm male adpter. At 11mm maybe the shortest 360º phototube ever, still 1mm off (Nikon 1 would be perfect, m4/3 2mm off because off flange distance) but I can live with that. Eyepieces and camera are parfocal

Image

Afocal ; the eyepiece sits on a M42 to M25 adapter inside a M42 tube, the Nikon SC has a M25-ish thread, goes inside and sits there centred without moving.
It sits parfocal with the eyepieces (slightly of, mm or so) via diferent adpters until I find the right length.
Then is placed as close as possible (touching) the Konika hexanon 40 1.8 focused to infinity and adapted to the Sony NEX, would work if it was not because of the middle hot spot I get. A modern 40mm would probably work better

ImageImage

Nikon SC eyepiece as photo eyepiece; same set up as afocal but without the Konica, placing the camera so I do not get vigneting but magnification is kept as low as possible (1.7X). Could probably fine tune it

ImageImage

I would advice people against looking like crazy for nikon SC scopes, I just used what I had available, maybe a more modern nikon or mitutoyo eyepiece works better. I still do not get the difference between eyepieces, relay lenses and teleconverters.. so I try them all

Best quality is always going to be direct projection, no matter how good a lens is it always will add some aberrations but for those times when optics just do not have enough reach may be a valid solution.

Javier

viktor j nilsson
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#7 Post by viktor j nilsson » Wed Mar 24, 2021 1:08 pm

Seta wrote: The Nikon SC has some kind of corrective lens after the objectives (pre infinity era prototype?? :mrgreen: ), so I figured out the eyepiece would be quite neutral
Image
If I remember correctly, this lens is basically a common rear element for all the objectives. Without it, they are useless. I think Nikon did this to make the objectives less desireable to steal in a classroom setting.


Seta wrote: Nikon SC eyepiece as photo eyepiece; same set up as afocal but without the Konica, placing the camera so I do not get vigneting but magnification is kept as low as possible (1.7X). Could probably fine tune it
I see. I have never tried to do this. I imagine you need to refocus a bit? Really surprised it worked so well.

Seta
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#8 Post by Seta » Wed Mar 24, 2021 5:33 pm

viktor j nilsson wrote:
Wed Mar 24, 2021 1:08 pm
If I remember correctly, this lens is basically a common rear element for all the objectives. Without it, they are useless. I think Nikon did this to make the objectives less desireable to steal in a classroom setting.
...
I see. I have never tried to do this. I imagine you need to refocus a bit? Really surprised it worked so well.
It was hard to remove that element, I wanted to test the 4x as a spotting lens for fishing in petri dishes, WD is about 40mm

I came across this old thread which says you are supposed to separate it 5mm or so, is not better to keep system parfocal? If this was going to be my final set up I would buy a M42 Helicoid for precise eyepiece placement. Maybe I get one just to run some tests (15€ aprox)


I just run another test stack, this time butterfly scales with nikon CF Fluor 20/0.50 and Nikon SC 1.7x "photo eyepiece", I would not normally use BF for a butterfly wing but was a nice exercise. I would say performance is pretty good corner to corner.

Image

Full size link

I do not think quality will be better than a proper CF PL2X but maybe is a good reminder of testing what we have around before start buying stuff like crazy.


EDIT: Just a little update, I was trying the Apo 40/1.0 oil with the Nikon SC and I did not like the quality, so I double checked and the camera was not parfocal. So I start playing rising and lowering the camera and the eyepiece and managed to get it parfocal without vigneting at 1.85X magnification (I guess there is not only one right setting). Maybe the OEM eyepiece was affected because of this, if I could manage to make it work I could get less magnification because it has wider field of view.

Now everything is parfocal, camera and eyepieces. I will make a new stack tomorrow to check if it performs better this time.
Is parfocality a sign the system is right even tube length may have changed?

Scarodactyl
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#9 Post by Scarodactyl » Wed Mar 24, 2021 11:04 pm

Oops, I had a post written up but it looks like I didn't actually press submit.
These results are really odd, to the point that I'm kind of wondering if there's something in the Olympus head that's having an effect--maybe that window at the bottom is doing something? Having flashbacks to using an infinity BHM with mitutoyos via direct projection and getting poor results because of subtle compensations in the tube lens which ruined the corners. Normally most higher end Nikon objectives should give at least reasonable corners on aps-c via direct projection.

Seta
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#10 Post by Seta » Wed Mar 24, 2021 11:16 pm

Scarodactyl wrote:
Wed Mar 24, 2021 11:04 pm
Normally most higher end Nikon objectives should give at least reasonable corners on aps-c via direct projection.
Direct projection works well and it is best in the test, I am just looking for a way to magnify the image when the subject is too small to fill up the frame. Something between 1.25x and 2x max, so far this nikon SC eyepiece works well as a photoeyepiece but I will have to rum more tests with different lenses.

Scarodactyl
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Re: Neutral eyepieces for projection or afocal method with nikon CFNs? Test added

#11 Post by Scarodactyl » Wed Mar 24, 2021 11:28 pm

Ah, I misunderstood, thought you mentioned extreme corners on direct projection underperforming.
With that in mind I definitely don't know what's going on. I'd think maybe the Konika happened to interact particularly well with the SC eyepiece and not with the OEM, but that wouldn't explain why it does so well without the lens too. Weird but very cool, and potentially very handy for aps-c Nikon users who don't want to modify their microscope's head for direct projection.
My optiphot is long gone or I'd try it myself.

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