Test, using Teleconverters and/or extension tubes on a microscope (I found what was wrong)

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seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

Adalbert wrote:
Sat Mar 13, 2021 12:43 pm
But your setup is probably CAMERA ->TC -> RING -> TL -> INF-LENS
as in the following picture:
Yes, I use it that way; but with bellows instead of tubes.

I had a kenko 1.4X that suffered from hot spot, I do not know about newer ones.

For me the TC is something to use just in the rare situations you may need it. The reason I am testing them now is because corner performance on some finite lenses is not the best, which is the kind of lens I will bve using in my scope most of the time.
I would like to add a projection lens, but low power one; these edmund optics achromatic doublets are a serious candidate.

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Adalbert
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Adalbert »

OK, I have never tried that before!
But I have a helicoid in my setup,
so I could adjust the length of the tube if needed.
And I will test my KENKO :-)
Best,
ADi

Scarodactyl
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Scarodactyl »

seta666 wrote:
Sat Mar 13, 2021 12:45 pm
Jotafoto and I bought a pair of U-TLUs a few years back, he adapted the lenses for me in a tube that fits inside chinese m42 tube. I only tried it in FF camera and performance was not good. I consists of several separate lenses (2 or 3), maybe got misaligned once he disassembled it. I will upload a picture later
The U TLU shows noticeable image degradation in APS-C corners vs the ultrawide head's tube lens so this seems like the expected result, no misalignment needed.

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

Thanks, at least I know i di not break it .. :D

Anyway, here are the pictures Pau wanted to see; is a pitty it did not work as expected, was a pretty neat set up.

U-TLU inside M42 tubes
Image

And the custom barrel for it

Image Image

Lou Jost
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Lou Jost »

But I have a helicoid in my setup,
so I could adjust the length of the tube if needed.
Remember not to alter your tube length; that needs to kept at the same length that was used without the TC. So your whole setup after adding the TC will now be longer than before.

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

I just made a very interesting discovery:

I was using the vivitar 1.5x TC nikon mount with a Nikon to Sony NEX adapter; which adds some extension (27mm) so you can use nikon lenses.

When using the teleconverter with the microscope I was getting a hot spot and magnification was more something like 1.8X ; adding a short extension tube removed that hot spot but increased the magnification to something like 1.9X

Making quick tests with my bellows and raynox tube lense I saw I was loosing infinity focus when used this way, I had to remove something close to 30mm extension to get infinity focus again. Same with the M42 one. I can not explain why this happens, maybe Rik can

I have placed the 1.5X teleconverter as close as I could to the camera and the hot spot has disappeared, corner performance has improved and magnification is 1.51X, very close to advertised 1.5X.

I do not have a short nikon to NEX adapter but a NEX to 52 male and 52 to 49 makes it stay in place, provisionally at least

Lou Jost
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Lou Jost »

I have placed the 1.5X teleconverter as close as I could to the camera and the hot spot has disappeared, corner performance has improved and magnification is 1.51X, very close to advertised 1.5X.
That's an important test of proper placement.

I am not sure I understand your set-up though. If the Nikon mount extension tubes +raynox + objective gave the objective's nominal magnification without trhe teleconverter, the exact same extension etc should give 1.5x the nominal magnification when mounted on the TC (with the TC mounted directly on the Nikon-Sony adapter.

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

Lou Jost wrote:
Sun Mar 14, 2021 6:51 am
I am not sure I understand your set-up though. If the Nikon mount extension tubes +raynox + objective gave the objective's nominal magnification without trhe teleconverter, the exact same extension etc shoul dgive 1.5x the nominal magnification when mounted on the TC (with the TC mounted directly on the Nikon-Sony adapter.
Nope, this is what common sense would suggest but it was not working. With the Nikon-Nex adapter I was getting 1.8x magnification instead of 1.5X; I was getting a hot spot in the middle of the frame, poor corner performance and infinity focus on the raynox was lost by 30mm
Now with TC almost inside the camera magnification is 1.51X, no Hot spot, good corner performance but Raxnox infinity focus is still lost by 15mm.

Maybe the ideal set up would be moving the TC inside the bellows, or do it via extension tubes.

Have you doble checked your tube lens keeps infinity focus with the TC? Corner performance even with the wrong set ups was OK with mitutoyos, bad with finite lenses.

Here you can see the two set ups

Image Image

An a 15.1X on sensor partial stack of a cheap educational slide( too cheap) with nikon CFN 10/0.30 plus 1.5X TC on Olympus BHT with NEX-5N

Image

Full size

And 100% crops (center and down left/ top right corners); Pmax, Pmax with CAs fixed in camera raw before stack, and then both with Levels and little sharpening in Photoshop

Image

This is the best performance I have been able to get from TC until now; bear in mind the CFN is not a mitutoyo.

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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by rjlittlefield »

seta666 wrote:
Sun Mar 14, 2021 6:33 am
<focus shifts with teleconverter> I can not explain why this happens, maybe Rik can
I cannot explain what you're seeing. I agree with Lou Jost about how the system should work.

When used as intended, the action of a teleconverter is pretty simple. Imagine you have a lens held in a fixed place, with the camera mounted directly on the lens, creating a focused image on the sensor. Then inserting the teleconverter moves the sensor farther back, while maintaining focus on the sensor in its new position, and making the image larger by the power of the teleconverter. Whatever the lens was focused on without the teleconverter, it remains focused on the same thing with the teleconverter.

If your system does not work this way, then I suppose it means that the teleconverter is not properly adapted to match the camera. I have no experience with Nikon-NEX adapters, so I have no idea what can go wrong there.

--Rik

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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Pau »

seta666 wrote:
Sat Mar 13, 2021 1:25 pm
Thanks, at least I know i di not break it .. :D

Anyway, here are the pictures Pau wanted to see; is a pitty it did not work as expected, was a pretty neat set up.
U-TLU inside M42 tubes
...
Thank you very much.

Does the male dovetail dismounts from the barrel unscrewing the bolts (I know that the female does)
If so, does it implies dismounting the lenses at risk of losing its right position?

Yes it's a pity, I was thinking in incorporating one to convert a finite microscope to infinite substituting the Oly dovetails with Zeiss ones, and direct projection on APSC was one of the goals.
I do so mounting a Sigma LSA on bellows in place of the microscope head but this is not convenient for use with at a trinocular head.
Would be better to look for a Oly head.
Pau

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

rjlittlefield wrote:
Sun Mar 14, 2021 11:44 am
I cannot explain what you're seeing. I agree with Lou Jost about how the system should work.
Although I have not used teleconverters with normal lenses I know how they are supposed to behave but I do not know why I getting this behaviour, with two different TC (Both the Vivitar 1.5X and the M42x).

To summarize these are the steps I take, I can not see anything wrong other than maybe a 1mm off because of the NEX-52 male adapter I use with the bellows and other mm with the adapter that connects teleconverter to bellows ( The TC to bellows mm can be corrected reducing extension by 1mm)

This is with infinity system:
- Focus the raynox mounted on bellows to infinity
- Remove camera
- Add teleconverter and NEX adapter; both the M42 and the Nikkon are the kind of adapter that allows focusing to infinity manual lenses
- Infinity focus is lost on the raynox; to get it back I have to reduce the bellows extension by 27-30mm (with both TC)

With the BHT finite microscope:

- Magnification I get with NEX adapters is 1.8X with 1.5X teleconverter and 2.4X with the 2X Teleconverter is. There is a overall drop in performance with both TC, worse in the corners.

- Next thing I tried is removing the nikon-NEX adapter and place the camera as close to the TC as possible; I would rate extension as 1-2mm

Now on the microscope the 1.5X TC works at 1.51X, overall performance still drops compared to direct projection but image is more balanced (center vs corners) and the 1.5X TC does not produce hot spot in the middle of the frame.

On the bellows I just need to remove is 15mm instead of 30mm to get infinity focus

With the infinity lenses I can just refocus the raynox to infinity (should be enough, right?), problem is the microscope with finite lenses.

I did run other test because this thing puzzles me; with Nikon BD Plan 40/0.65 (Higher NA than the 10 I tested before). 50mm extension added to the BHT phototube to get to those 210mm needed. TC with no adapter as discussed here. Subject is a printed piece of paper

Image

100% Crops, just levels adjusted. Both images aligned in Photoshop.
Image

Pmax files without TC and with TC
Last edited by seta666 on Sun Mar 14, 2021 1:01 pm, edited 1 time in total.

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

Pau wrote:
Sun Mar 14, 2021 12:12 pm
Does the male dovetail dismounts from the barrel unscrewing the bolts (I know that the female does)
If so, does it implies dismounting the lenses at risk of losing its right position?
Yes it's a pity, I was thinking in incorporating one to convert a finite microscope to infinite substituting the Oly dovetails with Zeiss ones, and direct projection on APSC was one of the goals.
I do so mounting a Sigma LSA on bellows in place of the microscope head but this is not convenient for use with at a trinocular head.
Would be better to look for a Oly head.
I do not have the U-TLU bottom part with me; Jotafoto has to send it to me. The top part has 3 screws; there are some spacers too.
Now that I am active again and when this covid situation relaxes a bit we may meet if you want. I can lend it to you so you can test it but
Raynox lenses offer better overall quality in my opinion.
Image

Dovetail is the same as BH-2; I bought Raf´42mm dovetail to M42 adapter to M42 and I will adapt the top part of the U-TLU to M42; this will allow me to use any M42 based tube lens with the BHT; M42 will also make it easy to adjust the length to get them focused to infinity I also bought a M26 to BHT turret, so I can use the mitutoyos; only one at the time.

Pau
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by Pau »

seta666 wrote:
Sun Mar 14, 2021 12:59 pm
...Now that I am active again and when this covid situation relaxes a bit we may meet if you want.
It will be a pleasure, of course
Pau

JKT
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by JKT »

The only explanation I can think of is the teleconverter is faulty and would not retain the infinity focus behind normal lenses either. My Kenko 1.4x did affect autofocus, so it likely had same issue to some extent.

seta666
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Re: Test, using Teleconverters and/or extension tubes on a microscope

Post by seta666 »

I just found an old Nikon 35-80mm laying around. Tried it with the 1.5xTC with the nikon-NEX adapter and works OK

I may be doing something wrong, I just do not know what it can be.

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