which 20x microscope optics to choose ?

[smugles]

Hello, I'm French, I'm a new member. I've been stacking photos for a few years, I'd like to improve. I have a request to make to you please:
I would like to have your opinion on microscope optics: I'm looking for a 20x infinity (not too expensive...) and WD 10.4 minimum
- I searched on E-bay and it's not easy to find the M Plan 20x unless I look badly !
- I sold a generic Plan 20x 0.40 infinity WD 10.4 which gave "acceptable" pictures but without more... I have a 20X Nikon rms CF Plan 0.40 WD 3.1
so I can't stack on microminerals and I base my leisure activity on it only. No other use. Also my Nikon can't be used?
I have an APS/C- a DCR 250 on a Wemacro motorized stand
If you have in mind a lens to advise me?
I read this post too on this forum : 20x Microscope Objectives
thans for your help.

[aphi]

Isn't a 20x objective kind of pointless for most cameras, since the camera will outresolve the objective simply due to diffraction? Unless I misunderstood a bunch of things, at m=20, a sensor with a pixel pitch of say p = 5 µm would resolve p/m = 250 nm on the object side of the objective, which is a resolution it physically cannot reach.

[rjlittlefield]

smugles, welcome aboard!

20X and long working distance is a tough combination.

The gold standard is 20X NA 0.42 Mitutoyo M Plan Apo, but as you've noticed those are hard to find used, even in uncertain condition. The Mitutoyo M Plan objectives are also noted for being relatively fragile, so used units have to be carefully checked before finally accepting them.

I confess that I do not know a good inexpensive 20X objective. I will let other people chime in with recommendations.

Isn't a 20x objective kind of pointless for most cameras, since the camera will outresolve the objective simply due to diffraction? Unless I misunderstood a bunch of things, at m=20, a sensor with a pixel pitch of say p = 5 µm would resolve p/m = 250 nm on the object side of the objective, which is a resolution it physically cannot reach.

aphi, welcome aboard also!

20X NA 0.40 may be overkill with respect to the camera sensor, but the resolution on subject at NA 0.40 is still 1.6 times better than at the NA 0.25 that you would typically get with a 10X objective. It's the ability to resolve finer detail on the subject that drives people to ever larger NA. As a matter of optical design it is difficult to achieve both large NA and a wide field on subject, so large NA objectives are usually high magnification also. The increase in magnification is faster than the increase in NA, so high magnification almost always means "empty magnification" if you're pixel-peeping with a modern sensor. But still the resolution on subject is better with larger NA, so if you're interested in the subject more than you're interested in a tack-sharp image, then high mag is the way to go.

--Rik

[smugles]

Hello to you all and thank you for this uninteresting info.
Indeed my aps/c is only 18Mpx and the diffraction is very present! I have as option to change the reflex for an old version of Canon 90D model that displays 31Mpxfor for it's less diffraction.
I'm just stacking up for me and my friends. I know the Rolls is the Mitutoyo, do you have any clones to submit to me?
Without wanting to horrify you, the site Alibaba offers it. . . . What do you think?
Thank you for your help.

[chris_ma]

Indeed my aps/c is only 18Mpx and the diffraction is very present! I have as option to change the reflex for an old version of Canon 90D model that displays 31Mpxfor for it's less diffraction.

maybe I missunderstand something, but a higher pixel count will not help with diffraction at all (which is a term used for an optical limitation of the lens), but rather make it more apparent.
so if you have significant softness due to diffraction on a 18MP sensor, a 31MP sensor will not bring out more detail.

in other words, the only point to go to a higher resolution sensor is if you also get a higher resolution lens.

[lothman]

Hello to you all and thank you for this uninteresting info.

I hope the uninteresting is just a typing error

I'm just stacking up for me and my friends. I know the Rolls is the Mitutoyo, do you have any clones to submit to me?
Without wanting to horrify you, the site Alibaba offers it. . . . What do you think?
Thank you for your help.

There are several different versions and vendors of 95mm parfocal lenses like the Mitutoyos. Chris S did an excellent test of a seller:
viewtopic.php?t=45250
I did tests from this seller with the 10x what I can recommend, but not the 5x.

on the other hand on APS-C the 20x M Plan from Nikon should be OK, at least my version was (click big):
http://www.lolux.de/Lothar/20x_mplan_ni ... cessed.jpg

[Scarodactyl]

I tried the Motic clone (also sold under other names), would not recommend vs a mitutoyo unless it's real cheap. That might have been a poor representative copy but I have heard similar assessments from others.

[Chris S.]

Before we discovered Mitutoyo 20x/0.42 objectives, the go-to lens for 20x was the Nikon CF 20x/0.4 ELWD 210/0 objective. This was, and still is, quite a good lens. It has 10.5mm working distance. I see the BD version of this lens on eBay for $250. Item number is 203514239781.

A few notes on this lens:

• It is a finite objective, so don't mount it on a converging lens (aka "tube lens.") Rather, mount it on a bellows or an empty tube of air.
• It is an achromat, whereas the Mitutoyo is an apochromat; expect some chromatic aberration with this Nikon lens. This CA tends to appear as a purple fringe on high contrast edges. Focus stacking, with many subjects, diminishes CA.
• BD and regular versions of this lens are optically identical, so far as we know. If you get the BD version, you will need to block light from passing through the outer portions of the barrel--not a difficult thing to do.
• The ELWD specification is important--it stands for "Extra Long Working Distance," which is why it has 10.5mm of WD.
• The 210/0 specification tells you two things. The 210 part indicates that the objective's shoulder should be 200mm from your camera's sensor (10mm are deducted from the 220 indicated because you are not using a microscope eyepiece. The /0 part indicates that no cover glass is expected. I see some similar lenses that are / followed by a number greater than zero--do not use these for macro work. (Cover glass thickness does not matter for numerical apertures of 0.30 and below, but does for higher NA's such as 0.40.)
• There are some phase contrast versions on eBay, but I'd avoid them.

A random Alibaba lens is likely to look nice, but perform disastrously. The lens I tested, per Lothman's link, was made by a small company that cares about its reputation and--I believe--very much wants to make quality lenses. I once tested very pretty lenses that were more random and no-name: They were horrible.

There is, by the way, not much correlation between how good an objective looks and how well it makes images. Very true even for second-hand Mitutoyos. Some pretty ones are optical disasters, and some ugly ones make very good images.

--Chris S.

[Beatsy]

A random suggestion. Perhaps find a decent 10x objective instead, highest NA you can stand (given the effect on working distance) and use Topaz Gigapixel AI to up-sample the resultant image by 2x.

A good 10x objective should be easier to find (and you may already have one). A second-hand 10x Mitty can be found more often, and significantly cheaper than the 20x, for example.

Of course, Gigapixel will not increase resolution, but it does make resolved details much easier to see in an on-screen or print scenario. The added bonus is covering a larger FoV than a 20x objective would. Although it's a microscope-based application, I frequently use Gigapixel to increase the image scale of small diatoms captured at the physical limits of resolution for the objectives used. It works really well. I see no reason it wouldn't work in extreme macro too and I've used it a few times myself, but not often, for subjects like butterfly wing scales.

To re-iterate, Gigapixel does not increase resolution, but it does make it look increased. Perhaps that could meet your needs.

[smugles]

Hello to all of you, a very big thank you for your comments which helped me to understand better some of my blockages because you were simple in your explications, pertinents and technical.

- Sorry my English is not very good and the translator makes mistakes: Indeed the informations received is very interesting!

Too bad there is no Nikon CF Plan WD 10.4! My generic "L Plan" was doing the job, but it is sold so I have to evolve. And sell now my nikon 20x WD 3.1 If you tell me : 20X and long working distance is a difficult combination.

=> I still have : the mitutoyo, a Nikon finite or infinite, or a Mity clone ....
=> the resolution of the 20X 0.40 is superior to a 10x Mitutoyo 0.25 that is to say that 20x will give less diffraction? Because yes, I'm looking for detail, not for empty magnification.

=> But if you were to compare:
-a 20X ELWD finished /
-a BD Plan finished /
-and a 20x CF Plan ∞/0
What would be your choice in terms of sharpness, chromatic aberration, flatness.... ? I'm not a technician nor a scientist in the study of photoghaphic lenses, but I would go with a 20x infinity, with what I've read, it would be slightly superior to the finite ones, but you in my shoes, what would be your choice between Nikon finite or infinity?


"The BD and standard versions of this lens are optically identical, as far as we know. If you go with the BD version, you'll need to keep the light from passing through the outer parts of the barrel, which isn't hard to do."
 That is to say? stop what? on my optics I have a black ring pierced with a certain diameter in the inner barrel? Are you referring to this?

=> I learned the differences between achro and Apo, I can "correct" a little chromatic aberrations with the LR editing software, but I don't use this function. Unless the defect is really visible.

I own a Nikon X10 CF plan 0.30 WD 16.5 For me it is EXTRA in terms of quality price = good ratio. However this idea of Gigapixel remains interesting, I did not know Topaz Gigapixel. But I will start on the purchase of a 20X preferably.


=> According to you my 18Mpx aps-c is correct for the X10 Nikon ? Or is it too small to take advantage of the optical qualities?
=> I was thinking of buying a 20MP reflex (Canon 7D) or even 24MP which would be largely sufficient for my use, I didn't want to buy the Canon 90D with very few shots for 500€ (1/2 price of new) last month... But if it brings out the diffraction even more, it's not good? Since I'm looking for "the sharpness" and I know that the sharpness is given by the lens, not the sensor.
=> So if I start with a 31Mpx = what do you think I'm starting with?

 I don't have 160 lenses anymore ... /0.17. But I just understood that they are annoying from apertures 0.40 and not below...


I received from a person, a comparison between a mitutoyo x5 and a copy from aliexpress, it make good job.
I give this link which is clean. Analyzed via Malwarebites if you are interested?

https://wetransfer.com/downloads/cc5290 ... 125/62eb14

Thanks a lot

[Chris S.]

Smugles,

Too bad there is no Nikon CF Plan WD 10.4!

This objective (or something very close to it) does exist. See page 14 of this 1989 Nikon brochure, under Plan Achromat>Long-Working-Distance/Dry> CF Plan N Plan Achromat ELWD 20 X. You will find a 20x objective with a numerical aperture of 0.4 and a WD of 10.5mm. For a photo that includes this lens, see the fifth photo from the top here.

I still have : the mitutoyo, a Nikon finite or infinite, or a Mity clone

If you can afford a brand new Mitutoyo from an authorized dealer, just buy it. There is no other “known-to-nearly-always-be-good” lens for macro work at 20x that has as little chromatic aberration.

Second-hand Mitutoyo objectives that look very nice to the eye, can produce disastrous optical results. (This is probably because a internal glass element has been knocked out of precise alignment. Such problems can not be repaired.) A lot of the “bad” Mitutoyo objectives are on the second-hand market; some knowledgeable forum members estimate that 60 percent of Mitutoyo objective on the second-hand market are bad. Conversely, I have never seen a bad Mitutoyo direct from an authorized dealer. (I’ve tested many Mitutoyo objectives for forum members; buying one of these in used condition can save you money, but only if someone can test it for you before you keep it.)

I think you should avoid Mituotyo “work-alikes” unless someone can test your individual lens for you and return it if it isn’t good. There are probably no true Mitutoyo “clones”--if "clone" means same glass, same elements, same custom building. Some companies offer Mitutoyo “work-alikes” that have the same thread size and parfocal distance. The known-to-be-good brands of these are almost as expensive as Mitutoyo, and usually not quite as good.

I think you should also avoid Mitutoyo work-alikes from no-name or little-known makers unless someone can test your lens for you. Some of the no-names I've tested were optical disasters. One maker I know of has made an excellent 20x Mitty workalike that I have tested. It’s even a bit better than the Mitutoyo. But I can’t speak for any other lens they make without testing it myself. Buying a no-name Mitutoyo-like objective without testing is like playing Russian roulette.

When a person is getting into high-magnification photography for the first time, it’s easy to make bad images for a while, even with a good lens--there are many issues to overcome. You will want to know that your lens, at least, is not a problem.

A Nikon finite or infinite—achromat, not apochromat—will be not quite as good in working distance or chromatic aberration as a Mitutoyo, but still pretty nice. And these are less prone to bump damage, so they can more safely be purchased on the used market.

 

But if you were to compare:

-a 20X ELWD finite /
-a BD Plan finite /
-and a 20x CF Plan ∞/0

What would be your choice in terms of sharpness, chromatic aberration, flatness.... ? I'm not a technician nor a scientist in the study of photoghaphic lenses, but I would go with a 20x infinity, with what I've read, it would be slightly superior to the finite ones, but you in my shoes, what would be your choice between Nikon finite or infinity?

For clarity, I’ve edited your word “finished” to “finite.”

If you mean a 20x BD Plan ELWD finite with the same working distance and numerical aperture as the regular, non-BD finite, you should see no difference in optical performance between the two. So far as we know, they are the same arrangement of glass elements. The BD is the same arrangement of glass, but in a somewhat different metal barrel.

As to whether the infinite version differs from the finite in performance, I have no idea. But the infinites were made later, so might have gained from improved glass types, manufacturing innovations, and improved coatings. Or maybe not. They were engineered for similar work, so are, in large strokes, similar.

"The BD and standard versions of this lens are optically identical, as far as we know. If you go with the BD version, you'll need to keep the light from passing through the outer parts of the barrel, which isn't hard to do."

That is to say? stop what? on my optics I have a black ring pierced with a certain diameter in the inner barrel? Are you referring to this?

“BD” stood for “Brightfield/Darkfield.” So in addition being useful for specimens that light shining through them from the back (darkfield), they made provision for shining light on the frontside of the subject (Brightfield). To do this, a cylinder of empty air was placed around the cylinder containing the glass elements of the lens. Some microscopes could shine light down this outer barrel and onto the subject.

If you place such a lens on a bellows or tubes, that empty barrel will let light enter your camera around the microscope objective, fogging your images. So you block this outer barrel with something opaque. This is easy to do.

=> According to you my 18Mpx aps-c is correct for the X10 Nikon ? Or is it too small to take advantage of the optical qualities?
=> I was thinking of buying a 20MP reflex (Canon 7D) or even 24MP which would be largely sufficient for my use, I didn't want to buy the Canon 90D with very few shots for 500€ (1/2 price of new) last month... But if it brings out the diffraction even more, it's not good? Since I'm looking for "the sharpness" and I know that the sharpness is given by the lens, not the sensor.
=> So if I start with a 31Mpx = what do you think I'm starting with?

I don’t think you will find big differences between 18MP, 20MP, and 24MP Cameras. With so little difference among pixel counts, I would choose between these cameras based on other features. However, if there is no other difference that you care about, by all means choose the 24mp camera. I use a Nikon camera with an APS-C 24MP sensor in the macro studio.

As to the question of where each sensor’s resolution becomes limited by a given combination of an objective’s magnification and numerical aperture, I’ll leave answering that to others.

I own a Nikon X10 CF plan 0.30 WD 16.5

That is very good working distance for a 10/0.30 objective. And a numerical aperture of 0.30 captures enough information to look really good at 10x.

For comparison, among well-made lenses, resolution scales linearly with numerical aperture. So an NA 0.40 lens will deliver about 1/3 more resolution than an NA 0.30.

A good 20x long-working distance objective typically has an NA of around 0.40.

So counter-intuitively, good 20x images often look “softer” than good 10x images. This is because the brain sees, in the 20x image, only one-quarter as much of the subject as in the 10x image. Other way of saying this is that the subject detail in the 20x image is 400 percent bigger than it was in the 10x image. But this 400-percent bigger detail has only 33 percent more information. So while the 20x image will have more resolution than the 10x image, it may be perceived as “less sharp.”

Photomicroscopists know this. Also, the 10x-20x transition is where I seem to start noticing the phenomenon, and to my eye, it gets worse with each higher doubling of magnification above that.

This is where Beatsy’s mention of Topaz Gigapixel AI intrigues me. As he points out, Gigapixel does not increase resolution. But making resolution “look” increased might decrease the visual penalty for zooming in and showing the viewer more information.

I don't have 160 lenses anymore ... /0.17. But I just understood that they are annoying from apertures 0.40 and not below...

If I understand you correctly: Objectives designed for cover slips, bearing the designation “/0.17” are a problem for use without coverslips if the numerical aperture is 0.40 or higher, and not a problem if the numerical aperture is 0.30 or lower.

If so, this is true. The issue is spherical aberration, which scales to the fourth power of numerical aperture. If graphed out, it’s clear that in practical use it can be treated as a step-function: at NA’s around 0.30 and below, forget about what cover glass an objective is rated for; but at higher NA’s, pay careful attention to this.

I received from a person, a comparison between a mitutoyo x5 and a copy from aliexpress, it make good job.

In high-end optics, there is a great deal of hand assembly. Among the many glass elements that make up our objectives, there is a surprising amount of individual variation in manufacturing. So the hand assembly of these elements involves mixing and matching, human judgment, optical testing, and offsetting one glass element’s virtues against another element’s vices. Then there is shimming and alignment of these elements.

I am not convinced that a test of a single objective from a little-known, small-volume lens maker can be assumed to apply to other lenses made by that maker, even if those lenses are of the same design.

I have tested many Mitutoyo objectives. Never have two individual objectives—even new from the factory--been identical in optical performance. New specimens are always very good, but differ in their tradeoffs. One might have slightly higher center resolution, while another has less center resolution but maintains resolution better toward the edges. Another may have higher contrast, but a little more chromatic aberration. I’m sure that the people who hand-assemble these lenses understand these tradeoffs, and perhaps spend years learning the art of it.

So I don’t think it useful to read too much into a test of a single lens specimen that was hand-assembled by its maker specifically to be tested at this forum. Even if the lensmaker has very fine intentions, I would want further testing on additional specimens to assess sample variation.

--Chris S.

[aphi]

Isn't a 20x objective kind of pointless for most cameras, since the camera will outresolve the objective simply due to diffraction? Unless I misunderstood a bunch of things, at m=20, a sensor with a pixel pitch of say p = 5 µm would resolve p/m = 250 nm on the object side of the objective, which is a resolution it physically cannot reach.

aphi, welcome aboard also!

20X NA 0.40 may be overkill with respect to the camera sensor, but the resolution on subject at NA 0.40 is still 1.6 times better than at the NA 0.25 that you would typically get with a 10X objective. It's the ability to resolve finer detail on the subject that drives people to ever larger NA. As a matter of optical design it is difficult to achieve both large NA and a wide field on subject, so large NA objectives are usually high magnification also. The increase in magnification is faster than the increase in NA, so high magnification almost always means "empty magnification" if you're pixel-peeping with a modern sensor. But still the resolution on subject is better with larger NA, so if you're interested in the subject more than you're interested in a tack-sharp image, then high mag is the way to go.

--Rik

Thanks for the warm welcome! Thanks for the explanation, I indeed completely missed that just because the sensor is "bottlenecked" by the magnification doesn't mean the spatial resolution of the entire system is limited at that point.

[chris_ma]

I indeed completely missed that just because the sensor is "bottlenecked" by the magnification doesn't mean the spatial resolution of the entire system is limited at that point.

I might understood the term "bottlenecked by the magnification".
In my view, the term magnification by itself doesn't define anything about resolution. to illustrate with ludicrous theoretical examples. we have two well matched setups:

A) lets say I have a 150MP FF sensor (2.4um pixel size) with an stunning 1x lens that can resolve 150MP on the sensor (meaning it resolves about 2.4um on the subject side)
B) on the other hand I have a 6MP FF (12um pixel size) sensor with a mediocre 2x lens that can resolve 6MP on the sensor (meaning it resolves about 6um on the subject side)

so the higher magnification setup has the much lower resolution.

now we switch the lenses on those two cameras:
C) the 2x lens (which resolves 6um on the subject) on the 150MP FF sensor (2.4um pixel size)
in this case, C will give about the same resolution as the example B (6um on the subject side), since the lens is a bottle neck.

D) and the 1x lens (which resolves 2.4um on the subject side) on the 6MP FF sensor (12um pixel size)
in this case, we'll only be able to resolve 12um on the subject side since the sensor is the bottle neck.

in reality, things are a lot more complicated, since resolution doesn't have any sharp cutoff, but is a curve that slowly diminishes.
the resolution of the total system is the product of all these curves (in digital imaging systems usually: lens resolution * sensor resolution * bayer filter)

[chris_ma]

ps: here an example of the product of lens MTF and sensor MTF (from edmundoptics Imaging Electronics 101: Camera Resolution for Improved Imaging System Performance):

[Pau]

This has been discussed several times, for example in this thread:
viewtopic.php?f=25&t=43827

The 20X I use for macro is the Oly LMPlanFl 20/0.40 UIS (modern infinite for no cover glass, 12mm WD) With a 200mm tube lens it works very well on APSC at 22X. I don't think that it would cover FF nor match the performance of the Mitty but if you can find it at a reasonable price like I did I think that it is a serious option.