Test, using Teleconverters and/or extension tubes

[Seta]

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, all living subject were too small to even try taking a picture.
Taken with the vivitar 1.5X TC (x1.9). I am having a hard time finding stuff to photograph..


These are Zerene output images, I process filen 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 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


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.

Edit:

I found out this set up is wrong, I was not taking into account the differences in flange distance of Nikon vs NEX (46.5 vs 18mm) which is like adding extension.

I made a drawing of what it would be to focus a hypothetical 100mm tube lens, first without teleconverter and then with teleconverter showing what was wrong with my set up and how it should be done.



Good news I can fix it in my vertical set up, bad news is I can not use it on my scope; my phototube is now 11mm long and still 1mm off; TC should be placed 17.5mm inside the trinocular head.
The only native sony FE 1.4x teleconverter is 500€, not worth it without testing it first.

Javier

[Placozoa]

I greatly appreciate comparisons such as this.

Thanks.

It is really difficult to photograph a truly fair comparison, its not even easy to make a fair comparison even without photographing it. I would not be comfortable attempting it, but I learn a lot when I see people that know what they are doing do it. It looked to me like you made it from 40x to 76x without losing much, then the 100x was no good.

[Scarodactyl]

In my own testing the Nikon photo eyepieces seemed to add a little CA of their own, but my direct projection setup was having trouble covering aps-c (thanks to their weird lens setup on the UW head).

[Seta]

In my own testing the Nikon photo eyepieces seemed to add a little CA of their own, but my direct projection setup was having trouble covering aps-c (thanks to their weird lens setup on the UW head).

That is the problem with some finite lenses, some do not cover APS-C very well but some cover even full frame (Nikon M plan 60/0.70 ELWD),
This is why I am seriously considering a low power relay lens (1.25 to 1.33x); these edmund optics achromatic doublets are a serious candidate.

[Scarodactyl]

In this case it wasn't a limitation of the objectives but the UW head (which creates infinity space and then has a tube lens. The eyepiece tube lens easily covers 26.5mm uw eyepieces but the camera tube lens does not, I need to replace it.)

[Seta]

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 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 like 30mm extension to get infinity focus again (the nikon adapter adds 27mm extension). Same with the M42 one. I can not explain why this happens

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

Here you can see the two set ups; before with nikon NEX adpter and now camera as close to the TC as possible; 1.8X vs 1.51X



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
That vein is good to show performance corner to corner



Full size

And 100% crops; Pmax, Pmax with CAs fixed in camera raw before stack, and then both with Levels and little sharpening in Photoshop



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