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

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seta666
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Test, using Teleconverters and/or extension tubes on a microscope (I found what was wrong)

Post by seta666 »

Hi,
Just run a quick test on the BHT with Nikon CFN 40/0.70 on a NEX-5N; focus stacked
This is the subject, Pine polen grains (Thanks Pau!) from a water sample, with the TC (x1.9). I am having a hard time finding stuff to photograph.. :D
Image

These are Zerene output images, I process files in CR before stacking, I did remove CAs, maybe not so well in some examples. All cropped to match the 100X one, but sampled at the same 5mpx. The normal one is upscaled from less than 3mpx, the 100x downscaled from 16mpx (was not my intention, had that setting on CR and I did not realise)
(link) 40X used normal way
(link) 50X (x1.25) with 50mm extension tubes
(link) 76X (x1.9) with a 1.5X Vivitar TC plus short extension tube (to get rid a hot spot reflection)
(link) 100x(x2.5) with 50mm extension plus a 1.5X Vivitar TC plus short extension tube (to get rid a hot spot reflection)

Some 100% crops; levels adjusted and very little sharpening; focus was adjusted manually, so may be better adjusted in one or the other. So 4 crops to make up for this.
full size link
Image

Maybe better quality TC will give better results; adding extension does not seem to affect performance that much, I will try to do a test with a subject that fills the frame. TC plus extension may be a little to much..

I would love to see a similar test on a nikon microscope; direct projection vs the photo relay lens. I am pretty sure the results via direct projection will be better (how much I do not know), unless the eyepiece is performing some kind of corrections.

On the BHT with olympus lenses this test can not be made as direct projection is not possible.

Javier
Last edited by seta666 on Mon Mar 22, 2021 12:44 pm, edited 3 times in total.

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

Post by Pau »

subjet: it seems pine pollen grains, very widespread right now
Pau

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

Post by seta666 »

Thanks Pau, it seems so. All the live specimens in the sample were too small to even try taking pictures of them.

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

Post by Adalbert »

Hello Javier,
Very interesting story.
Have you tested TC with the microscope lenses corrected to infinity as Mitties?
If yes, what would you recommend for the crop 1.6 and TC 1.5x and Mitu 50x ?
TC.jpg
BTW, I have already used TC but with tele EF70-200L and Mitu.
Best,
ADi

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 9:51 am
...
Have you tested TC with the microscope lenses corrected to infinity as Mitties?
If yes, what would you recommend for the crop 1.6 and TC 1.5x and Mitu 50x ?
...
Yes, I have used TC with mitus, it works ok. Bear in mind that my teleconverters are a 1.5X vivitar nikon mount and a 2X M42 one, under 50$ for both.. :D Some 1.4X teleconverters produce hot spot in the middle of the frame, they say because of light bouncing back from the sensor to the lens. It happens with my 1.5X TC and with a more modern kenko 1.4X MC7 I had. with aperture wide open you could not see it but as you closed the iris this was more evident.

I am using Raynox tube lenses, I have 3 of them (125mm, 170mm and 208mm), plus Morfanon 172mm and olympus U-TLU 180mm ( I took it out of its frame and corner performance is so so)

You will need a tube lens, does not the canon work ok? even if corner performance is not good the TC should maybe fix that.
On my scope I have noticed a drop in performance in the corners, that is with finite lenses. I place the TC where the camera was..maybe I should move them around and see.

This one is from this week; Papilio blumei 48X Mitutoyo 20 +2x M42 TC and Raynox DCR-150, 48X on NEX-5N. 80 shots
Image

Full size

And a couple of old ones with canon 5D mkII:

Jumping spider shot at 17X plus a small crop with mitutoyo 10/0.28, morfanon 172mm and a cheap vivitar 1.5X TC

[url:https://live.staticflickr.com/7031/6702 ... 53eb_o.jpg]link[/url]

And the first time I tried this combination; compared Mitu 10/0.28+ morfanon+2xTC against Nikon BD plan 20/0.40
Nikon 20X
Mitu 18X

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

Post by Lou Jost »

The quality of the teleconverter makes a huge difference. I mainly use the recent-model 1.4x Nikon TC, and for infinity optics it produces results practically identical to switching to longer tube lens. For finite objectives I think the TC may be better than using extension beyond its designed value. That was the case with my tests of the Nikon TC vs extension on the Printing Nikkor, which I posted on this forum some years ago.

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

Post by Adalbert »

Hi,

Have I understood this correctly?

So, the TC is used as follows

- with a finite microscope lens => to shorten the tube length

- with a infinite microscope lens => as tube lens

If so, where is the best position of the TC for an infinite lens?

Best,
ADi

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

Post by seta666 »

Lou Jost wrote:
Sat Mar 13, 2021 10:46 am
The quality of the teleconverter makes a huge difference. I mainly use the recent-model 1.4x Nikon TC, ......................
And no hot spot? that is good too know. I do not use TC very often, so I do not thing I am going to invest in a modern one. I would like to get a relay lens for my microscope though, with less power like 1.25x or
1.33x Edmund has some but still waiting for an answer.
Adalbert wrote:
Sat Mar 13, 2021 11:35 am
Hi,

Have I understood this correctly?..
Nope,

With finite optics he keeps the tube length, and instead or adding extension uses the TC. But in my opinion for low NA lenses I would say is pretty save to push them up, I have used them like that all the time

With infinity lenses you have the tube lens still focused to infinity and then the TC

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

Post by Pau »

seta666 wrote:
Sat Mar 13, 2021 10:34 am
...plus Morfanon 172mm and olympus U-TLU 180mm ( I took it out of its frame and corner performance is so so)]
I would like to see how you mount both lenses, and in particular how to dismount the U-TLU and how to mount it in tubes or microscope head
Pau

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

Post by rjlittlefield »

seta666 wrote:
Sat Mar 13, 2021 11:52 am
With infinity lenses you have the tube lens still focused to infinity and then the TC
I am puzzled. In your tests, where is the extension tube?

Tube lens at infinity + extension + TC will not focus at infinity. Tube lens at infinity + TC + extension will not focus at infinity either, and in addition moves the TC away from its design point.

So it seems to me that by adding extension you have dragged the objective away from its design point. This worries me because NA 0.70 does not have much tolerance for that. Even simple spherical aberration grows as NA to the fourth power, so NA 0.70 is about 60 times more sensitive than NA 0.25 .

--Rik

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

Post by Adalbert »

Yes, a picture of the setup would be very helpful

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

Post by Lou Jost »

Have I understood this correctly?

So, the TC is used as follows

- with a finite microscope lens => to shorten the tube length

- with a infinite microscope lens => as tube lens

If so, where is the best position of the TC for an infinite lens?
No on both counts. A teleconverter is an image expander. It is designed to be a precise distance from the sensor and it expects to receive the image in a precise plane. For infinity objectives, it goes between the tube lens assembly (including required extension tubes if using a Raynox or something similar) and the camera. The teleconverter should be designed for your camera brand, because it projects the best image in the plane of the camera sensor. There are some film-era general-brand teleconverters like the famous Vivitar TC with incorporated helicoid, but these are not as good as brand-specific teleconverters.

For finite objectives, you should get the tube length right according to the objective's data, and then you should remove it from your camera and put the teleconverter on the camera, and put the extension tube + objective assembly on the teleconverter. Make sure not to mess with your extension settings. This is a great way to improve the corners of your images.

In other words, the TC doesn't replace anything. It goes between your camera and your lens assembly, whatever that might be.

One more thing, some camera makers used to make specific teleconverters for specific lenses or ranges of lenses. These are usually very good. Nikon used to make a TC-201 and TC-301; both are 2x teleconverters but the TC-301 is a very long-barreled design with a protruding front element, designed for longer telephoto lenses like the ones we typically use as tube lenses, down to the Micro-Nikkor 200mm. Among 2x converters, I think this one is the best. However, I prefer the 1.4x generally, because it doesn't appreciably degrade the image. Check lens compatibility before buying:
http://www.mir.com.my/rb/photography/co ... index6.htm
Last edited by Lou Jost on Sat Mar 13, 2021 12:46 pm, edited 2 times in total.

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

Post by Adalbert »

Hello Javier,
Until now I have used CAMERA -> TC-> TELE 200mm-> INF-LENS.

But your setup is probably CAMERA ->TC -> RING -> TL -> INF-LENS
as in the following picture:
TC_TL_RING.jpg
Best,
ADi

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

Post by seta666 »

Pau wrote:
Sat Mar 13, 2021 12:11 pm
I would like to see how you mount both lenses, and in particular how to dismount the U-TLU and how to mount it in tubes or microscope head
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
rjlittlefield wrote:
Sat Mar 13, 2021 12:20 pm
I am puzzled. In your tests, where is the extension tube?
...
Two different things..

- The tests are performed on the BHT with nikon finite lenses; I use both CFN (TL 160) and BD plans (TL 210) so I have a 50mm extension tube to swap between systems.

As it was a test I wanted to see how bad the drop in performance was, anyway there are the files for anyone to download and check

- On my bellows set up when using infinity lenses I would focus the TL to infinity and then add the Teleconverter if I want to.
But I have just found that if I add the x2 M42 TC using a M42-NEX adapter (the long ones designed to be used with M42 manual lenses) I have to remove 27mm extension from my bellows so the raynox stays focused to infinity.
Makes sense as I was getting something like 2.3X from that M42 2x TC, I wrongly assumed that infinity focus would be kept

Something similar must be happening with the vivitar 1.5X, but the problem with that one is that even with a long nikon-nex adapter I get a hot spot in the middle of the frame, I have to use a short NEX extension tube and that fixes the problem. That extension ring has a rectangular window, maybe is that what fixes those reflections.

I cropped the test results to fit those of the TC/EXT combo 100X; if we looked at the corners without cropping quality would be worse for sure, but just taking into account the part of the image I was interested in (The subject) results came out pretty similar.. pretty amazing for such a bad configuration if you ask me.. :D
Last edited by seta666 on Sat Mar 13, 2021 3:18 pm, edited 1 time in total.

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

Post by Adalbert »

Hello Lou,
Many thanks for the info!
BTW, I have KENKO DG C-AF 1.5X TELEPLUS MC. Is it OK?
Best,
ADi

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