MicrobeHunter.com Microscopy Forum

Posted: **Thu Jul 09, 2020 6:01 pm**

75RR wrote: ↑
Thu Jul 09, 2020 5:34 pm

What is the Numerical Aperture of the 20x objective?
[/quote]

It's 0.40

Louise

Posted: **Thu Jul 09, 2020 9:02 pm**

I don't think it is supposed to work. This is what microscopyu says: https://www.microscopyu.com/microscopy- ... ifications

Most manufacturers have now transitioned to infinity-corrected objectives that project emerging rays in parallel bundles from every azimuth to infinity.
These objectives require a tube lens in the light path to bring the image into focus at the intermediate image plane.
Infinity-corrected and finite-tube length microscope objectives are not interchangeable and must be matched not only to a specific type of microscope,
but often to a particular microscope from a single manufacturer.

Can you provide a photo of it

For explanations on aberrations see page 51 and subsequent pages of the following downloadable book: viewtopic.php?f=15&t=4731

Posted: **Thu Jul 09, 2020 9:25 pm**

Usually using an infinite objective as a finite or vice versa results in badly degraded performance but there are exceptions too.

Posted: **Thu Jul 09, 2020 9:29 pm**

75RR wrote: ↑
Thu Jul 09, 2020 9:02 pm
I don't think it is supposed to work. This is what microscopyu says: https://www.microscopyu.com/microscopy- ... ifications

Most manufacturers have now transitioned to infinity-corrected objectives that project emerging rays in parallel bundles from every azimuth to infinity.
These objectives require a tube lens in the light path to bring the image into focus at the intermediate image plane.
Infinity-corrected and finite-tube length microscope objectives are not interchangeable and must be matched not only to a specific type of microscope,
but often to a particular microscope from a single manufacturer.

Can you provide a photo of it

There's not much to see - it's just a (new) cheap Chinese lens from Ebay:

: Plan_x20_small.jpg (54.21 KiB) Viewed 8224 times

I wonder how they specify the infinity objectives and tube lenses for the cheaper microscopes? How interchangeable are they for unbranded scopes?
I was trying to get some idea of the sort of distortions I might see? Do you know if there are any side-by-side images comparing them anywhere? I'm just trying to get a feel for things.

Thanks
Louise

Posted: **Thu Jul 09, 2020 9:35 pm**

Most of them seem to follow the broad strokes of Olympus infinity objectives: rms thread, 45mm parfocal and 180mm tube lens. But as to finer points of parfocality and such I am not sure how compatible they would be.

Posted: **Thu Jul 09, 2020 9:49 pm**

FWIW Here's a brightfield image of some pollen taken with the objective in question:

: Pollenx20_EP_camera33pc.jpg (45.47 KiB) Viewed 8222 times

I wish I had another instrument to compare but it's similar to images tagen with the x40, just smaller, of course!

Louise

Posted: **Thu Jul 09, 2020 11:27 pm**

That's a pretty dismal image. Tons of spherical aberration and increasing off axis ca.....especially for a 20X of only .4 N.A., which should have some resistance to spherical aberration due to the low N.A. Reports of people using infinity objectives in finite systems successfully and visa versa are not very common and a lot of them have to be taken with a grain of salt. Usually it is with lower N.A. objectives where sometimes it is difficult to see the effect of spherical aberration.I do know of some instances but not many.

There are not a lot of differences between made in China objectives within the two broad categories of 160mm or infinity. They are very good at changing the barrels and using the same optical formulas in many barrel styles. It gives the consumer the impression that there are all these choices and all this technology in what are essentially very basic microscopes but in reality they are just choosing barrel styles and a few other irrelevant features that any decent microscope should have.

Posted: **Fri Jul 10, 2020 5:23 am**

Have you taken them apart or something like that to confirm that? Or more just from testing samples and getting the same performance? It'd love to hear more about that (though it may deserve its own thread).

Posted: **Fri Jul 10, 2020 10:58 am**

apochronaut wrote: ↑
Thu Jul 09, 2020 11:27 pm
That's a pretty dismal image. Tons of spherical aberration and increasing off axis ca.....especially for a 20X of only .4 N.A., which should have some resistance to spherical aberration due to the low N.A. Reports of people using infinity objectives in finite systems successfully and visa versa are not very common and a lot of them have to be taken with a grain of salt. Usually it is with lower N.A. objectives where sometimes it is difficult to see the effect of spherical aberration.I do know of some instances but not many.

There are not a lot of differences between made in China objectives within the two broad categories of 160mm or infinity. They are very good at changing the barrels and using the same optical formulas in many barrel styles. It gives the consumer the impression that there are all these choices and all this technology in what are essentially very basic microscopes but in reality they are just choosing barrel styles and a few other irrelevant features that any decent microscope should have.

Well it's only a cheap plan achromat to start with. Sorry the image was a bit dim... Anyway I've just taken this one with the 10x (NA=0.25) 160mm Non Plan Achromat (the one that came with the scope so many years ago!) which I've cropped to approximate a similar size, and another using the 40x (NA=0.17) Plan Achromat 160mm (from same Chinese source):

10x:

: Pollenx10_bright_crop.jpg (55.58 KiB) Viewed 8184 times

40x:

: Pollenx40_EP_33pc.jpg (57.3 KiB) Viewed 8184 times

They are probably each as bad as one another but it least it shows some sort of comparison.
Louise

Posted: **Fri Jul 10, 2020 11:00 am**

Scarodactyl wrote: ↑
Fri Jul 10, 2020 5:23 am
Have you taken them apart or something like that to confirm that? Or more just from testing samples and getting the same performance? It'd love to hear more about that (though it may deserve its own thread).

I would have thought that one could confirm it is an infinity objective by removing the microscope head and holding a paper over the light beam that it produces.
An infinity objective would produce a parallel beam, which would have the same diameter as you raise and lower the paper,
while a finite objective would focus to a point, producing a variable diameter circle on the paper.

Posted: **Fri Jul 10, 2020 11:30 am**

LouiseScot wrote: ↑
Thu Jul 09, 2020 4:57 pm
I've never quite understood exactly what a tube lens does in terms of aberration and maybe also colour correction?
Thanks for any expertise/advice

Here is a compact description of the difference :
"Handbook of Biological Confocal Microscopy, Volume 236" edited by James Pawley, pages 156-157 (viewable on the internet, without downloading, when I google "infinity optics vs 160mm tube lens" or similar).
EDIT:
https://books.google.co.il/books?id=E2m ... on&f=false

Posted: **Fri Jul 10, 2020 11:42 am**

Hobbyst46 wrote: ↑
Fri Jul 10, 2020 11:30 am
Here is a compact description of the difference :
"Handbook of Biological Confocal Microscopy, Volume 236" edited by James Pawley, pages 156-157 (viewable on the internet when I google "infinity optics vs 160mm tube lens" or similar.

I think you need to allow for different browsers etc ... I had no luck in my search using your suggested parameters.

Since you have obviously found the link, why not just post it?

Posted: **Fri Jul 10, 2020 11:45 am**

75RR, thanks for the idea. Done.

Posted: **Fri Jul 10, 2020 12:24 pm**

Hobbyst46 wrote: ↑
Fri Jul 10, 2020 11:45 am
75RR, thanks for the idea. Done.

Hi

Um, the particular page isn't viewable. In any case, comparing the finite and 'infinity' objectives by using them as magnifying glasses doesn't show any obvious differences plus I'm obviously getting an image without any kind of tube lens. It's possible that it's just incorrectly marked as an infinity lens? It only cost me £45 via an Ebay seller last year. Perhaps someone could kindly point me to a source of better quality 160mm plan achromats? It might be worth trying out another one. At the end of the day, there is really just the objective lens and the camera, from an imaging point of view.
Thanks

Louise

Posted: **Fri Jul 10, 2020 12:29 pm**

In any case, comparing the finite and 'infinity' objectives by using them as magnifying glasses doesn't show any obvious differences ...

Just turn on your microscope as you would normally do, focus on a slide, then take off the head and place a paper over the light beam from the 'infinity' objective.

Move it up and down to see if the diameter of the beam changes.

Do the same with a 160 objective to see if there is a difference. The diameter should change using the 160 as you raise and lower the paper.

Posted: **Fri Jul 10, 2020 12:42 pm**

75RR wrote: ↑
Fri Jul 10, 2020 12:29 pm

In any case, comparing the finite and 'infinity' objectives by using them as magnifying glasses doesn't show any obvious differences ...
No need for a magnifying glass, just turn on your microscope as you would normally do, focus on a slide, then take off the head and place a paper over the light beam from the 'infinity' objective.

Move it up and down to see if the diameter of the beam changes.

Hi
I didn't use a magnifying glass - just used the objectives as if they were magnifying glasses. Using the 20x, doing the projection on to a piece of paper gives a changing circle of light which comes into focus at a point above the head - I'm guessing at ~160mm! Same with 10x finite objective. So I really need better quality finite objectives from somewhere...
Louise

Posted: **Fri Jul 10, 2020 12:49 pm**

LouiseScot wrote: ↑
Fri Jul 10, 2020 12:24 pm
...At the end of the day, there is really just the objective lens and the camera, from an imaging point of view.

It ain't necessarily so. On the BX50 imaging system showed above, I believe that it was the objective, tube lens and camera; if one had used the dedicated Olympus camera like the DP70, DP73 etc, it would be the objective, tube lens and camera, plus a reducing lens between the camera and tube lens (optional, to cover a larger portion of the FOV).
Yet there are other options in hobby use, for example, for finite (160mm) tube optics : (1) objective + camera body; (2) objective + eyepiece + camera body; (3) objective + eyepiece + camera lens + camera body (aka afocal). Each of which may be the winner in image quality, depending on the equipment.

Posted: **Fri Jul 10, 2020 12:50 pm**

Hobbyst46 wrote: ↑
Fri Jul 10, 2020 12:49 pm

LouiseScot wrote: ↑
Fri Jul 10, 2020 12:24 pm
...At the end of the day, there is really just the objective lens and the camera, from an imaging point of view.
It ain't necessarily so. On the BX50 imaging system showed above, I believe that it was the objective, tube lens and camera; if one had used the dedicated Olympus camera like the DP70, DP73 etc, it would be the objective, tube lens and camera, plus a reducing lens between the camera and tube lens (optional, to cover a larger portion of the FOV).
Yet there are other options in hobby use, for example, for finite (160mm) tube optics : (1) objective + camera body; (2) objective + eyepiece + camera body; (3) objective + eyepiece + camera lens + camera body (aka afocal). Each of which may be the winner in image quality, depending on the equipment.

I was just talking about my setup

Louise

Posted: **Fri Jul 10, 2020 1:47 pm**

Might one of these be better than I have:

https://www.ebay.co.uk/itm/Nikon-Micros ... Sw-s5ePDkq

Or would there actually be little in it? I read a post on here from 2016 ("Better objectives for a Chinese microscope") where the poster substituted a Nikon CFN Plan x40 for his Omax objective and there didn't seem to be a great deal in it! Are all finite plan achromats pretty much the same? Maybe I would be better off just getting a new scope complete with, hopefully, better objectives, after all?

Louise

Posted: **Fri Jul 10, 2020 2:07 pm**

Maybe I would be better off just getting a new scope complete with, hopefully, better objectives, after all?

It is true that the objectives are the heart of a microscope, but you do have to place them in a 'good' stand.

The one you have is not going to do them justice.

If you want to get some nikon objectives then fine, but also get a Nikon stand.

All the other bits that you will need such as a condenser and eyepieces and anything else you want is available and compatible.

That is the beauty of a modular system, everything you need is designed to work well together. No guesswork, no bodging.

I know you are not overly keen on used but they are affordable, originally cost many thousands of pounds and you can return it if it is not as described.

Posted: **Fri Jul 10, 2020 2:29 pm**

LouiseScot wrote: ↑
Fri Jul 10, 2020 12:42 pm
...Using the 20x, doing the projection on to a piece of paper gives a changing circle of light which comes into focus at a point above the head - I'm guessing at ~160mm! Same with 10x finite objective. So I really need better quality finite objectives from somewhere...

Although the reproducibility of quality of images from new unbranded objectives has been questioned, I doubt that they went so far as to mark a finite optics objective with the "infinity" sign...

Posted: **Fri Jul 10, 2020 3:28 pm**

Hobbyst46 wrote: ↑
Fri Jul 10, 2020 2:29 pm

LouiseScot wrote: ↑
Fri Jul 10, 2020 12:42 pm
...Using the 20x, doing the projection on to a piece of paper gives a changing circle of light which comes into focus at a point above the head - I'm guessing at ~160mm! Same with 10x finite objective. So I really need better quality finite objectives from somewhere...
Although the reproducibility of quality of images from new unbranded objectives has been questioned, I doubt that they went so far as to mark a finite optics objective with the "infinity" sign...

It is strange but the objective behaves as a finite one. I don't think the UK based Ebay supplier normally even offers infinity objectives. Perhaps it was one in a 'bad batch'. I could ask the supplier but I bought it over a year ago now so would feel a bit silly!
Louise

Posted: **Fri Jul 10, 2020 3:50 pm**

75RR wrote: ↑
Fri Jul 10, 2020 2:07 pm

Maybe I would be better off just getting a new scope complete with, hopefully, better objectives, after all?
It is true that the objectives are the heart of a microscope, but you do have to place them in a 'good' stand.

The one you have is not going to do them justice.

If you want to get some nikon objectives then fine, but also get a Nikon stand.

All the other bits that you will need such as a condenser and eyepieces and anything else you want is available and compatible.

That is the beauty of a modular system, everything you need is designed to work well together. No guesswork, no bodging.

I know you are not overly keen on used but they are affordable, originally cost many thousands of pounds and you can return it if it is not as described.

I was going to only get the one Nikon objective just to try, to compare. I don't know why the make of stand would make a huge difference when the objective is just being used like a camera lens. The stand I have is fine for 160mm objectives although the focus resolution isn't as good as I'd like (I'm sure a Nikon stand would be better for that!), but with only achromats, it's probably ok. I could probably do with a better camera. The one I have is ok-ish (It's a Touptek 5M with Aptina sensor and 2.2um pixels) but tends to be a bit grainy.
Louise

Posted: **Fri Jul 10, 2020 5:05 pm**

LouiseScot wrote: ↑
Fri Jul 10, 2020 3:50 pm
...I could probably do with a better camera. The one I have is ok-ish (It's a Touptek 5M with Aptina sensor and 2.2um pixels) but tends to be a bit grainy.

If the camera is an eyepiece camera, so is being used without eyepiece, the Nikon CF objective is expected to perform very well, since it is inherently corrected for aberrations.
Regarding the previous images you posted - can it be that the viewing eyepieces and the camera were not exactly parfocal ? I am using an eyepiece camera from time to time, each time I install it have to carefully adjust parfocality.
The Toupview software is very good, IMO.

Posted: **Fri Jul 10, 2020 5:26 pm**

Hobbyst46 wrote: ↑
Fri Jul 10, 2020 5:05 pm

LouiseScot wrote: ↑
Fri Jul 10, 2020 3:50 pm
...I could probably do with a better camera. The one I have is ok-ish (It's a Touptek 5M with Aptina sensor and 2.2um pixels) but tends to be a bit grainy.
If the camera is an eyepiece camera, so is being used without eyepiece, the Nikon CF objective is expected to perform very well, since it is inherently corrected for aberrations.
Regarding the previous images you posted - can it be that the viewing eyepieces and the camera were not exactly parfocal ? I am using an eyepiece camera from time to time, each time I install it have to carefully adjust parfocality.
The Toupview software is very good, IMO.

Yes it's a small EP type camera. It's only parfocal if I actually use it in place of an eyepiece. Usually, I use it in the trinocular position. In either case I'll use the monitor screen to focus on. The pollen is probably not the best subject as the grains are opaque and 3d.
Louise

Posted: **Wed Jul 22, 2020 1:19 pm**

This was a very informative post - like everything in a nutshell.

Louise, what have you decided at the end? I am also a fan of the Motic BA310 or BA410. There are online shops selling it from EU too. The BA410 would be around 3000Eur including transport etc. and it is a bit above average.

Anyway, I just wanted to ask if you have decided.

Steve.

Posted: **Wed Jul 22, 2020 1:34 pm**

I would support some of the advice already given in this thread: one should stay the heck away from Chinese scopes. Compared to a used scope from the big four/five makers from 80ies or even 70ies, the Chinese new scopes are expensive garbage. Quality/price ration is very different.

Posted: **Wed Jul 22, 2020 2:25 pm**

FungusMan wrote: ↑
Wed Jul 22, 2020 1:19 pm
This was a very informative post - like everything in a nutshell.

Louise, what have you decided at the end? I am also a fan of the Motic BA310 or BA410. There are online shops selling it from EU too. The BA410 would be around 3000Eur including transport etc. and it is a bit above average.

Anyway, I just wanted to ask if you have decided.

Steve.

Hi Steve

I replied to this earlier but it seems to have disappeared! In a nutshell, I'm looking again at the Euromex Oxion now - plus with some higher power objectives upgraded to plan fluors. The BA410 is too expensive for me. Even the Oxion with upgraded objectives will be about £2000. I'm skipping phase contrast for now. Most of the Chinese infinity corrected scopes seem to be compatible with Olympus infinity spec but the cost of their brand objectives is prohibitive. After all, this is only a hobby/pastime for me and I don't do very much of it anyway.

Louise

Posted: **Wed Jul 22, 2020 3:51 pm**

The Chinese infinity microscopes are patterned after the 3 of the microscope systems they have been asked to make the cheaper optics for. Each objective type is usually produced in 3 versions. Olympus pattern, with a 180mm reference length, Nikon R.M.S with a 200mm reference length and Nikon 60mm parfocal with a 200mm reference length.

There are also a few designs that appear to be possibly purchased or swiped from other discontinued systems. The ones I have seen look unique and are usually on some more expensive equipment.

Posted: **Thu Jul 23, 2020 11:09 am**

apochronaut wrote: ↑
Wed Jul 22, 2020 3:51 pm
The Chinese infinity microscopes are patterned after the 3 of the microscope systems they have been asked to make the cheaper optics for. Each objective type is usually produced in 3 versions. Olympus pattern, with a 180mm reference length, Nikon R.M.S with a 200mm reference length and Nikon 60mm parfocal with a 200mm reference length.

There are also a few designs that appear to be possibly purchased or swiped from other discontinued systems. The ones I have seen look unique and are usually on some more expensive equipment.

Yeah, most objectives that I've looked at - Euromex Oxion, Motic and AmScope seem to be of the Olympus 180/45mm variety.

Louise

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