More confusion about Nikon trinocular head

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pippo1234
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More confusion about Nikon trinocular head

#1 Post by pippo1234 » Fri Feb 05, 2021 2:47 pm

HI,

I took the plunge and got a UW trinocular head. I set it up with the 2.5x relay lens inside and the camera is out of focus with the stage all up (specimen still too far from objective). After some headscratching and tinkering I retry without the lens at the bottom of the phototube (see attached picture). The camera is now perfectly focused at the same objective-specimens distance as my binocular head. I cannot check right now whether it's also parfocal with the eyepieces in the UW head as I don't have any 30mm eyepiece yet. I assume so though.

What am I missing about the purpose of that lens?

Many thanks,
Giulio

Image

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blekenbleu
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Re: More confusion about Nikon trinocular head

#2 Post by blekenbleu » Tue Aug 02, 2022 5:21 pm

Probably too late to help you, but Ichthyophthirius addressed this:
https://www.photomacrography.net/forum/ ... p?p=206784

Your initial issue with the 2.5x relay lens was, perhaps,
wrong distance between that CF PL2.5X and the camera's sensor.
Trying with the photo lens but without that photo port tube lens
(which was missing in my UW head) had not occurred to me; thanks!
Metaphot, Optiphot 1, 66; AO 10, 120, EPIStar, Cycloptic

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Re: More confusion about Nikon trinocular head

#3 Post by Lomonaut » Mon Aug 08, 2022 8:27 pm

Well, you got it working :D

I would be interested in some pictures taken with your setup, as I also have a Nikon UW trino head (on an Optiphot) and was considering the same PL2.5x projection eyepiece. A different head though, see photo. I think it has a positive lens at the bottom, f = +/- 200 mm.

I'm now leaning towards direct projection (get rid of the chimney with a grinder?), live view on a screen is better for my neck anyway ;)
Attachments
UWhead1.jpg
UWhead1.jpg (111.36 KiB) Viewed 5613 times

Sure Squintsalot
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Re: More confusion about Nikon trinocular head

#4 Post by Sure Squintsalot » Mon Aug 08, 2022 9:09 pm

I just went through this a few days ago. I removed the chimney innards and just rested my camera on top the open tube. I do have an adapter that securely nests inside the tube, however.

Photos are now way less hazy and camera FOV is very close to eyepiece FOV. Less than a quarter turn separates eyepiece focus from camera live view focus. I'm much happier with this setup, though now I have that chimney and a 2.5x TV lens sitting around.

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Re: More confusion about Nikon trinocular head

#5 Post by blekenbleu » Mon Aug 08, 2022 10:53 pm

Sure Squintsalot wrote:
Mon Aug 08, 2022 9:09 pm
I just went through this a few days ago.
I removed the chimney innards and just rested my camera on top the open tube.
I do have an adapter that securely nests inside the tube, however.

Photos are now way less hazy and camera FOV is very close to eyepiece FOV.
Less than a quarter turn separates eyepiece focus from camera live view focus.
I'm much happier with this setup, though now I have that chimney and a 2.5x TV lens sitting around.
That echoes my experience with a type F head, but neither for UW nor T.
A type F head, when twisted for photos, allows a unobstructed shot from objectives,
provided that accessories (e.g. vertical illuminator half-mirror) are out of the way,
with images on ground glass parfocal with oculars at around 190mm distance above BD Plan objectives.
UW or T heads have nearly the opposite of an infinity tube lens at their bottom dovetail,
which gets cancelled by the lens in @Giulio's image,
as well as one in the optical path to binocular eyepieces:
Image
With UW trinocular guts and chimney removed, a ground glass shows a usefully focused image near the port
with 20x or 40x 210/0 objectives. That image gets larger (and of course dimmer) with raised ground glass,
so not really infinity, which by my understanding would not focus any image on ground glass.
With e.g. 5x objective, there is no useful image until ground glass is about 25cm above the gutted UW photo port,
but field of view is very much cropped from that in WF10x/23 30mm oculars.
Images for a 10x BD Plan objective focus more nearly like those for 5x than 20-40x.
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Re: More confusion about Nikon trinocular head

#6 Post by Scarodactyl » Tue Aug 09, 2022 12:06 am

Yeah, the provided lens vignettes on aps-c, but if you replace it with a similar ~100mm fl lens it works better.

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Re: More confusion about Nikon trinocular head

#7 Post by blekenbleu » Tue Aug 09, 2022 2:31 pm

Scarodactyl wrote:
Tue Aug 09, 2022 12:06 am
replace it with a similar ~100mm fl lens
If "it" is the lens at the bottom of what Brooke Clarke calls the camera tube:
Image
https://www.prc68.com/I/Labophot.html#Trinocular_type-T
...then my impression is that Giulio simply removed it.

FWIW, my UW trinocular head was received with no camera tube lens.
Not expecting to ever obtain such a lens, seemingly different from that in T camera tubes,
I have been trying to unscrew the bottom section of that camera tube from the top two sections,
so far unsuccessfully, presumably because of thread locking compound applied by Nikon during assembly.
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Re: More confusion about Nikon trinocular head

#8 Post by Scarodactyl » Tue Aug 09, 2022 3:56 pm

If you want the original dealcorner had a whole uw chimney with lens, might still. But it isn't a particularly special lens, just a ~100mm doublet which also vignettes. I have one also without a chimney which I need to finish up. I got a 95mm nikon lens that almost fits in, just needs a protruding bit filed down. Hand held in place the results were good.

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Re: More confusion about Nikon trinocular head

#9 Post by Sure Squintsalot » Tue Aug 09, 2022 4:50 pm

I removed all of this:
Screenshot 2022-08-09 103732.jpg
Screenshot 2022-08-09 103732.jpg (25.38 KiB) Viewed 5507 times
And simply sat my camera on top of the chimney. There is an Fotodiox adapter on the camera, which is just an empty tube that acts as both spacer and holder for a sleeve that better secures the camera to the tube:
Screenshot 2022-08-09 103810.jpg
Screenshot 2022-08-09 103810.jpg (68.81 KiB) Viewed 5507 times
The image plane in camera is very flat and matches pretty closely what I see through the eyepieces, though focusing is off by some small amount. It would be nice to machine, or 3D print a spacer that mates to the camera body, matches eyepiece focus and threads onto the chimney, but that's a project far off the horizon.

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Re: More confusion about Nikon trinocular head

#10 Post by blekenbleu » Tue Aug 09, 2022 9:22 pm

Sure Squintsalot wrote:
Tue Aug 09, 2022 4:50 pm
The image plane in camera is very flat and matches pretty closely what I see through the eyepieces, though focusing is off by some small amount.
Based on what I saw with ground glass, that seemingly could work for 20X and higher objectives, but not 5X...
I guess that is your SONY NEX-5 body without lens and am baffled.
Last edited by blekenbleu on Tue Aug 09, 2022 10:17 pm, edited 1 time in total.
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Re: More confusion about Nikon trinocular head

#11 Post by blekenbleu » Tue Aug 09, 2022 10:06 pm

Scarodactyl wrote:
Tue Aug 09, 2022 3:56 pm
I have one also without a chimney which I need to finish up.
I got a 95mm nikon lens that almost fits in, just needs a protruding bit filed down.
Hand held in place the results were good.
I am inspired by your Surplus Shed doublet experiment to try something similar
for full UW image circle on camera sensor without vignette, but Nikon's 50mm thread is a challenge;
I have tried heating the camera tube to unscrew that section, as yet unsuccessfully...

That does not diminish my curiosity about what is working for Sure and Giulio!
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Re: More confusion about Nikon trinocular head

#12 Post by Scarodactyl » Tue Aug 09, 2022 11:03 pm

I need to pick up another optiphot so I can test this properly. The ss doublet gave great results as far as I remeber bht I didn't rigorously test it.

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Re: More confusion about Nikon trinocular head

#13 Post by Sure Squintsalot » Wed Aug 10, 2022 4:18 am

blekenbleu wrote:
Tue Aug 09, 2022 9:22 pm
Sure Squintsalot wrote:
Tue Aug 09, 2022 4:50 pm
The image plane in camera is very flat and matches pretty closely what I see through the eyepieces, though focusing is off by some small amount.
Based on what I saw with ground glass, that seemingly could work for 20X and higher objectives, but not 5X...
I guess that is your SONY NEX-5 body without lens and am baffled.
Works great with 5x M Plan Objective, as below. Note that in yellow on the Sony Nex 5 display is the focus assist, which does an admirable job helping to maximizing focus; note the uniformity of that yellow field across the display indicating a pretty flat field. The depth of field (what's yellow vs. what is not) is a few tens of microns:
Screenshot 2022-08-09 220851.jpg
Screenshot 2022-08-09 220851.jpg (105.09 KiB) Viewed 5450 times
The system works just as well with the M Plan 10x:
Screenshot 2022-08-09 221140.jpg
Screenshot 2022-08-09 221140.jpg (99.19 KiB) Viewed 5450 times
With the 40x objective, the focus assist has a tougher time with the lack of sufficient edge contrast, so, I have to magnify the display on the camera 4.5x or 9.6x to really dial it in:
Screenshot 2022-08-09 221431.jpg
Screenshot 2022-08-09 221431.jpg (97.25 KiB) Viewed 5450 times
At 100x, the DOF is only a few microns, according to the ticks moved on the focus dial. Nevertheless, the FOV remains flat and not substantially different than that seen through the eyepice:
Screenshot 2022-08-09 221714.jpg
Screenshot 2022-08-09 221714.jpg (84.77 KiB) Viewed 5450 times

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Re: More confusion about Nikon trinocular head

#14 Post by Scarodactyl » Wed Aug 10, 2022 5:34 am

I'll be honest, I am surprised it'a possible to focus without the lens in the light path.

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Re: More confusion about Nikon trinocular head

#15 Post by blekenbleu » Wed Aug 10, 2022 11:24 am

Likewise, but as soon as something mechanically engaging the UW port 50mm thread is sorted, I'll be trying it.
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Re: More confusion about Nikon trinocular head

#16 Post by blekenbleu » Wed Aug 10, 2022 8:03 pm

blekenbleu wrote:
Wed Aug 10, 2022 11:24 am
mechanically engaging the UW port 50mm thread
That will take awhile, so instead a mirrorless APS-C camera body was suspended from a copy stand
with an EF-M to M42 adapter and M42 extension tubes smaller than 50mm o.d.:
Image

As already reported, decent camera image quality is available.
With camera flange a few mm above the UW port,
diagonal field nearly matches WF10X/23 oculars.
Raising the camera further does not quickly defocus images
so much as increase magnification (and cropping).
While my BD Plan 210/0 objectives are not quite parfocal in oculars,
refocus among objectives for camera imaging is considerable
in this configuration, IMO. Other objectives might be less tolerant...
Experiments with available 35mm close-up lenses at roughly the same
distance as Nikon's intended camera tube lens will be attempted next.
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Re: More confusion about Nikon trinocular head

#17 Post by viktor j nilsson » Wed Aug 10, 2022 8:10 pm

blekenbleu wrote: While my BD Plan 210/0 objectives are not quite parfocal in oculars,
refocus among objectives for camera imaging is considerable
in this configuration, IMO. Other objectives might be less tolerant...
This suggests that your sensor is located quite far from the correct position. Likely the image will be okay at 10x, but at 20x I think you'll start to see some quite pronounced deterioration, and at 40x the image should be quite bad. Since those achromats are quite low NA they'll be more tolerant to deviations in tube length than high-NA apos and fluorites, but you'll still start to get pretty bad aberrations at NA 0.65+.

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Re: More confusion about Nikon trinocular head

#18 Post by blekenbleu » Wed Aug 10, 2022 9:07 pm

viktor j nilsson wrote:
Wed Aug 10, 2022 8:10 pm
This suggests that your sensor is located quite far from the correct position.
agreed. https://www.photomacrography.net/forum/ ... 74#p272374
pretty bad aberrations.
The image above (and my highest magnification Optiphot objective) is 40X 0.65 n.a.;
I've been waiting for a cheap Plan 60X to appear...
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Re: More confusion about Nikon trinocular head

#19 Post by blekenbleu » Thu Aug 11, 2022 3:14 pm

pippo1234 wrote:
Fri Feb 05, 2021 2:47 pm
What am I missing about the purpose of that lens?
To answer the original question, assuming that UW and T photo tube lenses differ in diameter, but not focal length,
then with parts shown in Sure's Screenshot 2022-08-09 103732.jpg,
a mirrorless camera sensor will be parfocal with oculars when elevated above a UW "chimney" by about 135mm:
Image
Image on the above LCD is by magnified Live View for more critical focusing

That unintuitively large 135mm separation is because Nikon designed CF PL relay lenses to allow space
for inserting elaborate optics and sensor to compose and adjust exposures for film.
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Re: More confusion about Nikon trinocular head

#20 Post by Scarodactyl » Thu Aug 11, 2022 4:41 pm

Oh, if the image is far from parfocal without the second lens then it's just a matter of refocusing the system so the lens which is supposed to be focusing to infinity focuses closer instead. That makes sense but is probably i troducing aberrations to the image.

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Re: More confusion about Nikon trinocular head

#21 Post by Sure Squintsalot » Thu Aug 11, 2022 5:35 pm

blekenbleu wrote:
Thu Aug 11, 2022 3:14 pm
That unintuitively large 135mm separation is because Nikon designed CF PL relay lenses to allow space
for inserting elaborate optics and sensor to compose and adjust exposures for film.
That'd make sense...I've seen those intermediate viewers that get installed above the chimney, and they add some distance to the light path on its way to a 35mm film plane. Maybe 135mm?
Scarodactyl wrote:
Thu Aug 11, 2022 4:41 pm
Oh, if the image is far from parfocal without the second lens then it's just a matter of refocusing the system so the lens which is supposed to be focusing to infinity focuses closer instead. That makes sense but is probably i troducing aberrations to the image.
I didn't think this system ever focused to infinity, but yeah, I'm a big fan of removing as much glass between subject and sensor (as long as things are flat and focused). In this case, non-parfocality between eyepiece and camera causing me to re-focus for the camera isn't that big a deal.

If I were to video live, fast moving organisms, I'd want precisely parfocal eyepiece and sensor, unless the camera was tethered to a computer. You guys helped me better understand what all of that hardware was for; thanks!

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Re: More confusion about Nikon trinocular head

#22 Post by blekenbleu » Thu Aug 11, 2022 5:53 pm

At least for Nikon 210 BD and M Plan objectives that I have tried, whether refocusing without photo tube lens
yields image artifacts worse than those from parfocal photo tube lens + CL PL2.5X relay is unobvious.
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Re: More confusion about Nikon trinocular head

#23 Post by blekenbleu » Thu Aug 11, 2022 6:04 pm

Sure Squintsalot wrote:
Thu Aug 11, 2022 5:35 pm
to video live, fast moving organisms, I'd want precisely parfocal eyepiece and sensor
For cameras with HDMI output, a television works best for fine focusing with my old eyes.
I have yet to source parfocal shims for BD Plan objectives; changing magnifications is always a hassle.
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Re: More confusion about Nikon trinocular head

#24 Post by Scarodactyl » Fri Aug 12, 2022 12:55 am

Yeah, theoretical issues aside all that matters is what you can get away with. Sometimes it's more than raw theory would predict.

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Re: More confusion about Nikon trinocular head

#25 Post by blekenbleu » Fri Aug 12, 2022 1:54 pm

For completeness, here is a trinocular T photo tube lens with about 82mm separation from mirrorless camera body:
Image
.. yielding APS-C images parfocal with UW WF10X/23 oculars:
Image
.. that unexpectedly capture those oculars' full field of view.
Vignette in LCD display is from Optiphot field illumination stop, also barely visible in oculars.
I read that UW photo tube lens diameter is larger than that for type T trinocular,
which evidently suffices for these oculars.

Sadly, cheap generic M42-M44 step-up rings are not readily available;
I find only Baader Zeiss M44 Female to T2 Female Adapter # T2-09 1508041
https://agenaastro.com/baader-zeiss-44m ... 08041.html
... with 49.5mm o.d. listed, which will not fit into type UW or T 50mm ports,
APM M44.5 to T2 Digiscoping / Projection Adapter https://astrograph.net/APM-M445-to-T2-Adapter,
and RAF camera M44x0.75 female to M42x1 male thread adapter https://rafcamera.com/adapter-m44x0-75f-to-m42x1m,
which would be a tight fit:
Image

This photo "field expedient" motivates more attempts at unthreading that UW photo tube bottom section
for use with a thin M52-M42 helicoid focuser.
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Re: More confusion about Nikon trinocular head

#26 Post by blekenbleu » Fri Oct 07, 2022 4:10 pm

Sure Squintsalot wrote:
Wed Aug 10, 2022 4:18 am
At 100x, the DOF is only a few microns, according to the ticks moved on the focus dial.
Nevertheless, the FOV remains flat and not substantially different
Unsurprisingly, impact of tube length error on aberrations has been modeled and experimentally quantified.
One widely cited model is Gibson - Lanni:
https://opg.optica.org/josaa/viewmedia. ... &html=true

This plot for interesting numeric apertures:
Image
... was made based on (mis?)understanding second-hand discussion here:
https://www.photomacrography.net/forum/ ... 45#p258045
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Re: More confusion about Nikon trinocular head

#27 Post by Sure Squintsalot » Tue Oct 25, 2022 8:47 pm

Hmmmmmm....

I thought I understood that graph, but I guess I don't.

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