Evaluating potential microscope objective upgrades.

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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apochronaut
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Evaluating potential microscope objective upgrades.

#1 Post by apochronaut » Wed May 20, 2020 12:02 am

By far the most economical way of improving one's microscope is to purchase objective lenses that have improved performance, when compared to the ones being currently used. Microscope companies usually offer several to a great many choices and the easiest way of making an improvement is to buy one or more objectives that have been made as part of your microscope's accessory complement. They will give more or less guaranteed results but sometimes however, buying into the same stable is not practical : the objective(s) being sought may be rare, expensive or both.
An option , may be to purchase an objective made by another company that has the features one is looking for but exists either in greater quantities, is less expensive and frequently both go together.
Although there are many reasons one might seek an objective upgrade, the three most common ones are probably : 1) better planarity 2) better colour correction 3) better resolution , a by product of higher N.A. and superior colour correction.

One difficulty sometimes overlooked though, is that the differences between two objectives are differences in specification and a different specification requires different technique. While replacing an X brand 40X .65 achromat with an X brand 40X .65 planachromat might be a fairly simple swap, replacing an X brand 40X .65 achromat with a Z brand 40X .85 planfluorite might not be. The swap might entail an adaption as simple as having to open the condenser diaphragm more but in order to get the best results from an upgrade, you must meet it's specification requirements fully, so being on the watch for other quirks of your new toy, might save you some grief. Here are some things to keep in mind.

The following 4 sections are relevant to fixed tube systems and also mostly infinity systems. There are further comments about infinity systems at the end.

Switching Brands.
------------------------------ Each optic in a microscope is mated to the rest of the optics to create as perfect an optical system as possible within the economic confines of the instrument. The microscope is organized in a system and the system has discreet specifications. The system can be unique but almost all of them are in one of 3 groups. These groups or systems have lengths , based on the optical tube meaurement : 160MM, 170MM and infinity. Unless you know for sure that there is an optical compatability across systems, any ugrades should be from the same system.

Within each system, the various manufacturers over time have chosen a length for their objectives. This is called the parfocal length. Almost all of them are 33mm,34mm,35mm,36.5mm,37mm or 45mm. Again , unless you are sure that adapters will work to equalize parfocal lengths effectively, any upgrades should be of the same parfocal length. This is sometimes just a convenience issue, since rotating a nospiece with objectives of various lengths can raise the risk of equipment damage.

Many microscope systems require precision eyepiece/objective combinations in order to work well. Even though you have found the ideal objective , you also may need the ideal eyepieces specific to it, to keep it ideal.m



Switching Planarity or Plan field of view
----------------------------------------------------------------- The caution about a possible additional expense for compatable eyepieces is often due to the necessity for plan compensation, or sometimes negative compensation. This can even be the case when one is upgrading to plan objectives or apochromats of the same brand as the microscope stand. Without correct compensation, even if the field is flat it will likely be terribly full of chromatic abberration or other distortions, giving the impression that the improvement was not a worth while expense. Any upgrade must be complete.

Switching N.A.
------------------------- Higher N.A. objectives are almost always more finnicky about their requirements. They will need a higher N.A. of incoming light, so the condenser will have to be opened more than you may be used to opening it for a certain magnification, or even upgraded itself if the objective upgrade has an N.A. greater than the condenser's maximum. Coverslips will need to be more precise and possibly individually measured or pre-measured. You will also lose working distance, so some of those prepared go to slides , may not focus anymore. Many amateur, old , student or hobby slides have thicker than necessary cover slips and prove difficult to use with higher grade objectives.

Switching Colour Correction
----------------------------------------------- This is the most difficult one because as the corrections in the objective become more refined, it takes only very slight variances in the total system, to throw those corrections off. A little thing like .02 mm of cover slip can be enough to prompt an otherwise perfectly corrected plan achromat to display chroma near to the field border. Most highly corrected objectives also have high N.A.'s , so pampering that N.A. will do wonders towards making what might have been a big investment , a usefull investment. It is not unusual for an apo objective to perform beautifully in most of the field but lose corrections at the periphery, when it has been swapped into a non-original situation. It's a corrections mis-match and they don't usually show up within quite a distance off axis. Some think that is sign that the objective isn't designed well or might be faulty. A planapo or planfluorite, from any of the 8 or so brands that made them from 1980 on should correct faultlessly center to edge, with virtually zero residual ca.

With infinity systems the same precautions hold and although the systems are all infinity , the reference tube length is convergent and will have some corrections built in. With infinity systems it isn't eyepiece compatability that is the major concern, it is the overall corrections of the system, which includes the converging or telan lens . Generally, it isn't good practice to mix and match objectives from infinity systems but some known compatabilities exist. Even if a crossover objective seems to work, a different reference length will give a different magnification. When it comes to the corrections that are being used in the Chinese infinity systems , it seems that they have been ,,,,,uh,, borrowed, so the possibility of crossing some of them over to the more classic systems does exist. I have had some success but have run into considerable magnification differences: over 10%, higher too, which is odd given that it was 10% higher in a 180mm tube! Contrast has always been a problem, with the off brand or modern stencil brand objectives I have trialled and centering can be dreadfull.
With infinity systems there also have been several parfocal lengths, with all of them proprietary except the 45mm D.I.N. However, unlike fixed tube systems, due to the objective residing in the infinity part of the optical tube, a shorter objective can be lengthened with an adapter with no resulting alteration in it's corrections or magnification. That all happens from the telan lens northward.
Last edited by apochronaut on Wed May 20, 2020 7:47 pm, edited 3 times in total.

Sabatini
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Re: Evaluating potential microscope objective upgrades.

#2 Post by Sabatini » Wed May 20, 2020 2:33 am

Thank you for the virtual master classes

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Re: Evaluating potential microscope objective upgrades.

#3 Post by Scarodactyl » Wed May 20, 2020 2:47 am

Another great overview! This should be very helpful for people starting out.
apochronaut wrote:
Wed May 20, 2020 12:02 am
With infinity systems the same precautions hold and although the systems are all infinity , the reference tube length is convergent and will have some corrections built in.
It is important to note that a number of brands do not do any specific corrections in the tube lens or eyepieces. Nikon, Olympus (aside from the BH series infinity objectives of course), and Mitutoyo (plus clones like Optem) being the most important that spring to mind.

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Re: Evaluating potential microscope objective upgrades.

#4 Post by apochronaut » Wed May 20, 2020 10:34 am

I use the term corrections rather loosely, because in essence all lenses introduce distortions or aberrations to the incoming light, even if the ultimate result is to cancel out those that it introduces.
It would be interesting to see how a Mitutoyo, or Olympus or Nikon objective made it through the telan lens of one of the other brands? Have you ever tried any of these combinations?

I know that certain of those objectives are used as lenses for macrophotography.

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Re: Evaluating potential microscope objective upgrades.

#5 Post by viktor j nilsson » Wed May 20, 2020 11:23 am

apochronaut wrote:
Wed May 20, 2020 10:34 am
I use the term corrections rather loosely, because in essence all lenses introduce distortions or aberrations to the incoming light, even if the ultimate result is to cancel out those that it introduces.
It would be interesting to see how a Mitutoyo, or Olympus or Nikon objective made it through the telan lens of one of the other brands? Have you ever tried any of these combinations?

I know that certain of those objectives are used as lenses for macrophotography.
Yes, objectives from all of these makes have been used with many different tube lenses for macrophotography, here are some examples:
Olympus UMPlanFl 20X, Raynox DCR150 as tube lens:
https://www.photomacrography.net/forum/ ... ht=#254265

Olympus LMPlanFL 20x, Kenko AC CLOSE-UP No.5 as tube lens:
https://www.photomacrography.net/forum/ ... b872f51a3c

Mitutoyo 5x M Plan Apo, many different tube lenses:
https://www.photomacrography.net/forum/ ... hp?t=37740

Mitutoyo 10X M Plan Apo, different tube lenses:
https://www.photomacrography.net/forum/ ... hp?t=23898

Big test with: Nikon LU Plan 10X, Nikon CFI Plan Achromat 10x, Mitutoyo M Plan Apo 10X
Tube lenses: Thorlabs ITL200, Schneider 120mm f5.6 Makro-Symmar, Raynox DCR-250 (125mm)
https://www.photomacrography.net/forum/ ... hp?t=38363


To summarize: While some combinations definately outperform others, it is not always the brand-specific tube lens that performs best.

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Re: Evaluating potential microscope objective upgrades.

#6 Post by Hobbyst46 » Wed May 20, 2020 12:52 pm

apochronaut wrote:
Wed May 20, 2020 10:34 am
I use the term corrections rather loosely, because in essence all lenses introduce distortions or aberrations to the incoming light, even if the ultimate result is to cancel out those that it introduces.
It would be interesting to see how a Mitutoyo, or Olympus or Nikon objective made it through the telan lens of one of the other brands? Have you ever tried any of these combinations?

I know that certain of those objectives are used as lenses for macrophotography.
Some modern infinity-corrected-optics microscopes from the big 4 do not enable interchangeability of objectives among different brands, even because the objective threads are not the same.

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Re: Evaluating potential microscope objective upgrades.

#7 Post by apochronaut » Wed May 20, 2020 4:20 pm

That's true but there are adapters with which to use R.M.S. objectives on nosepieces that have metric threads of greater diameter and some to go the other way too. You can even adapt the old Jena 19mm thread up, to R.M.S. at least.
This doesn't entail any great problem, really. The pitfalls could be : the possibility of a mis-match in corrections ; a parfocal differential, likely solvable through the use of shims or collars and a smaller image circle that an R.M.S. objective might have and be unable to fill a very wide f.o.v. . In some cases, a differential in the location of the rear focal plane of an imported objective, either directly mounted or on an adapter could disable it's potential use with an intermediate optic. Those are all whole other issues but in general, there are work arounds for objective sizing mis-matches and the small extra distances involved do not affect infinity corrected optics, such as is the case with finite optics.

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Re: Evaluating potential microscope objective upgrades.

#8 Post by KD Arvidsson » Wed May 20, 2020 7:30 pm

Thanks for that lesson very interresting :) //KD
Microscope Nikon Labophot 2
Panasonic GH4 and HY-2307 Camera+Euromex adapter.
Westcoast of Sweden.
https://www.youtube.com/channel/UCjsgbq ... dyl2x0Atpw

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Re: Evaluating potential microscope objective upgrades.

#9 Post by apochronaut » Wed May 20, 2020 8:05 pm

viktor j nilsson wrote:
Wed May 20, 2020 11:23 am
apochronaut wrote:
Wed May 20, 2020 10:34 am
I use the term corrections rather loosely, because in essence all lenses introduce distortions or aberrations to the incoming light, even if the ultimate result is to cancel out those that it introduces.
It would be interesting to see how a Mitutoyo, or Olympus or Nikon objective made it through the telan lens of one of the other brands? Have you ever tried any of these combinations?

I know that certain of those objectives are used as lenses for macrophotography.
Yes, objectives from all of these makes have been used with many different tube lenses for macrophotography, here are some examples:
Olympus UMPlanFl 20X, Raynox DCR150 as tube lens:
https://www.photomacrography.net/forum/ ... ht=#254265

Olympus LMPlanFL 20x, Kenko AC CLOSE-UP No.5 as tube lens:
https://www.photomacrography.net/forum/ ... b872f51a3c

Mitutoyo 5x M Plan Apo, many different tube lenses:
https://www.photomacrography.net/forum/ ... hp?t=37740

Mitutoyo 10X M Plan Apo, different tube lenses:
https://www.photomacrography.net/forum/ ... hp?t=23898

Big test with: Nikon LU Plan 10X, Nikon CFI Plan Achromat 10x, Mitutoyo M Plan Apo 10X
Tube lenses: Thorlabs ITL200, Schneider 120mm f5.6 Makro-Symmar, Raynox DCR-250 (125mm)
https://www.photomacrography.net/forum/ ... hp?t=38363


To summarize: While some combinations definately outperform others, it is not always the brand-specific tube lens that performs best.
Yes, I am clear that those objectives can be used with various tube lenses with good results but this in no way indicates that the objectives do not require any corrections in the tube lens. Those tube lenses above, are all custom set ups and subject to being tested for performance. My question doesn't relate to that. It was whether anyone knows how Mitutoyo, Olympus or Nikon infinity corrected objectives would make it through one of the other brands telan lenses : meaning a Mitutoyo used with an Olympus telan lens and a Nikon through a Mitutoyo and so forth. If any of them at all do not work to the fullest capacity with another maker's telan lens, then either the objective requires corrections that the telan lens can't provide, or the telan lens is providing corrections that the objective doesn't need.

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Re: Evaluating potential microscope objective upgrades.

#10 Post by viktor j nilsson » Wed May 20, 2020 9:01 pm

I see what you mean, Phil. These tests do often use tube lenses in configurations that are different from what the manufacturer intended (different distance to sensor, reversed, etc). So they don't really answer your questions. And at least in some cases it seems like the "macro people" try to optimize different things than microscope manufacturers. For example, because macro photographers tend to stack their photos, they tend to favour configurations that minimize CA but increase field curvature, whereas for example Mitutoyo appears to favour configurations that achieve better field flatness at the expense of some CA.

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Re: Evaluating potential microscope objective upgrades.

#11 Post by PeteM » Wed May 20, 2020 9:32 pm

I've used Nikon infinity objectives (25mm mount, 60mm parfocal) on a Leica infinity stand (25mm mount, normally 45mm parfocal but plenty of focus and condenser distance to handle the extra 15mm). The magnification stays the same, because both are 200mm nominal tube lenses. One Leica DMLS is set up entirely with Nikon CFI60 objectives. I didn't see objectionable aberrations; but also haven't set up to take photos which would be a more exacting test.

Also have tried all sorts of infinity objectives on an Olympus BHS converted to infinity (BX type head adapted to it). Nice thing about the BHS is that spare nosepieces are readily available. Originally used this to compare Olympus A, DPlan, Splan, and SPlan Apo in the finite realm. Then realized it would be easy to convert a BHS to infinity.

Olympus UIS are, of course, excellent. Old Reichert infinity 40x Plan and 100x Plan Apo are quite good on both Olympus and Leica stands. Many other infinite versions, such as Leitz infinity no cover, work acceptably. The famous Nikon 20x Plan Apo infinity is also good; though not so good as on its native stand.

Generic Chinese infinity objectives work -- at least the 20x -- on Olympus infinity as well.

Never been able to justify Mitutoyo objective prices . . .

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Re: Evaluating potential microscope objective upgrades.

#12 Post by apochronaut » Wed May 20, 2020 10:37 pm

Could you post some unretouched comparative photos of some of these rearrangements? It would be educational for those looking to snag an inexpensive objective to make an upgrade with.

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Re: Evaluating potential microscope objective upgrades.

#13 Post by Scarodactyl » Wed May 20, 2020 11:19 pm

apochronaut wrote:
Wed May 20, 2020 8:05 pm
Yes, I am clear that those objectives can be used with various tube lenses with good results but this in no way indicates that the objectives do not require any corrections in the tube lens.
I think one could say that the tests indicate that any specific corrections are minor enough that random well-corrected lenses can match them very well, sufficiently well for serious photographers anyway. I think that's as close to not requiring specific corrections as you can get, given the weird voodoo that seems to happen with the very fine details of tube lens-objective interactions (whatever makes reversing, focusing past infinity in some cases, etc provide those fine scale benefits). Nobody seems to have found any third-party lenses that happen to match up to eg Zeiss or Leica corrections.

The one matchup I can share personal data on is more of an oddball: Leica/Wild uses a 200mm, apparently non-correcting tube lenses in the heads of their M-series stereos and macroscopes. I've put a Wild makrozoom objective onto a Nikon infinity head and as far as I could tell it performed identically to being attached to a Wild head, certainly no noticeable increase in CA or reduction in resolution in my test shots. I've used a Kenko 200mm lens (known to work well on Mitutoyos) as a tube lens on a Leica MZ95 with a planapo objective and as far as I could tell there weren't any noticeable aberrations from the combo, though I didn't do any really rigorous tests on that one. Similarly, famed mineral photographer Danny Sanchez uses Mitutoyo objectives coupled directly to his Wild M400 head and seems to get really exceptional results with that combination.

Mitutoyos seem to perform as well as Nikons on the Nikon ITL-200 tube lens which suggests compatibility there too.

From a zoomed-out perspective that seems to indicate at least passable (for photographic work, and thus probably for eye viewing) interchangeability between Wild/Leica stereo tube lenses, Mitutoyos and Nikons.

Sorry to push the conversation towards a more obscure point in relation to your original post, which I do think is an excellent and extremely helpful overview.

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Re: Evaluating potential microscope objective upgrades.

#14 Post by MichaelG. » Thu May 21, 2020 5:45 am

apochronaut wrote:
Wed May 20, 2020 8:05 pm
[...] My question doesn't relate to that. It was whether anyone knows how Mitutoyo, Olympus or Nikon infinity corrected objectives would make it through one of the other brands telan lenses : meaning a Mitutoyo used with an Olympus telan lens and a Nikon through a Mitutoyo and so forth. If any of them at all do not work to the fullest capacity with another maker's telan lens, then either the objective requires corrections that the telan lens can't provide, or the telan lens is providing corrections that the objective doesn't need.
Forgive me please [as one with negligible practical experience of ‘infinity’ microscopes) for jumping into this discussion:
First: I presume that the terms ‘telan’ and ‘tube lens’ can be safely interchanged; but please correct me if I have missed some subtle distinction.

Now: I am aware that some telans provide corrections that others do not, but I think we can safely say that [by definition] all ‘infinity systems’ share the concept of an ‘infinity space’ and that their telans are therefore processing a subject at infinity.

So: we do some ‘reverse engineering’ and test each manufacturers’ telan, as a simple long-focus lens ... no objectives or eyepieces required.
This should reveal any inbuilt corrections as apparent defects

MichaelG.
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Re: Evaluating potential microscope objective upgrades.

#15 Post by Scarodactyl » Thu May 21, 2020 7:17 am

It might not be that easy unfortunately.
https://www.photomacrography.net/forum/ ... hp?t=38202
Tube lens performance with non-compensating infinity objectives seems to not be strongly predicted by performance imaging directly at infinity focus, based on this test and other more anecdotal reports. That said I don't think I've seen any images taken at infinity with an ITL200 or through a Nikon head with no objectives, both of which sound like they'd be very interesting. Certainly nikon infinity heads provide views that look great to the eye, though they're a bit unwieldy as binoculars.
I don't know if that indicates there are cryptic corrections in Nikon tube lenses that these lens' deviations from ideal happen to match, or that the fine details of tube lenses in general are more complicated than expected.

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Re: Evaluating potential microscope objective upgrades.

#16 Post by MichaelG. » Thu May 21, 2020 8:09 am

Scarodactyl wrote:
Thu May 21, 2020 7:17 am
It might not be that easy unfortunately.
Thanks for the link, and your thoughts

What I suspect would be most informative would be to test a Zeiss tube-lens, which we know to have compensating corrections [*] as a ‘proof of concept’ ... it should perform rather poorly as a general purpose long-focus camera lens.

MichaelG.

.
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https://www.motic.com/As_News/n116.html
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Re: Evaluating potential microscope objective upgrades.

#17 Post by apochronaut » Thu May 21, 2020 12:31 pm

I can't do Zeiss but I can use a telan lens from the grandfather of all infinity systems going back to 1962: AO 34mm parfocal, also used by Reichert Austria from 1975 or so on for their short objective infinity microscopes. I have not photographed through one of those lenses used as a long focus lens but even just using a head as a pair of binoculars shows evident chroma around specular highlights, something not seen, or at least not readily seen with the eye when using a head from the 45mm parfocal system made from 1985 on by the same manufacturer. They clearly have altered the corrections in the objectives and therefore the corrective capacity of the telan lens. All I am easily seeing is ca. A photo might more easily detect coma, curvature of field etc. etc.

That's why when the 45mm parfocal 25X .65 planapo referenced above in my original post, was used in the older short objective system , it lost those very qualities that make it a stellar planapo and filled all the smaller interspaces of a particular diatom with a pinkish chroma. All of a sudden it isn't a highly corrected planapo anymore but to those unaccustomed to it's normalcy , it's malcorrect image might be seen as acceptable, about as good or still even better than an average achromat. It is sometimes difficult to determine how a lens in the system is affecting an achromat though, because all achromats and to a lesser extent fluorites give dirty images to varying degrees. Mal correction in the tube lens , most evidently shows up as chroma. If one is looking through an objective and sees some chroma, well that might be deemed acceptable, or pretty good, or any number of adjectives to describe a system that is o.k. . What if the system was not designed to be just o.k., based on someone's quick judgement ? What if It was designed to be excellent in it's class.
While photography has recently become a yardstick by which we measure a microscope's capability, with photography, one can correct for deficiencies of optical correction. So, while photography fixes image problems in time , turning the microscope image into something that can be perused for defects not seen casually , and in fact enhances certain defects like chroma, it also has compatible programs and much capacity to wipe them out, erase them; especially if they are subtle, or even crop them out.
That can't be done during observation. There is a whole class of microscopists , to which photography is a by path ; something relied on for future information, documentation mainly and relied upon to be faithful to the image, not distort it into a design for a shower curtain . Perfection of the image, the way the engineers and designers envisioned it is important to the microscopist to whom the collection of images and experiences in memory are important to his/her body of work and the optics need to work as intended, not be just acceptable, or o.k. or almost as good as.....

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Re: Evaluating potential microscope objective upgrades.

#18 Post by MichaelG. » Thu May 21, 2020 2:16 pm

apochronaut wrote:
Thu May 21, 2020 12:31 pm
I can't do Zeiss but I can use a telan lens from the grandfather of all infinity systems going back to 1962: AO 34mm parfocal, also used by Reichert Austria from 1975 or so on for their short objective infinity microscopes. I have not photographed through one of those lenses used as a long focus lens but even just using a head as a pair of binoculars shows evident chroma around specular highlights, something not seen, or at least not readily seen with the eye when using a head from the 45mm parfocal system made from 1985 on by the same manufacturer. They clearly have altered the corrections in the objectives and therefore the corrective capacity of the telan lens. All I am easily seeing is ca. A photo might more easily detect coma, curvature of field etc. etc.

[…]
Many thanks for that detailed comment ... it suggests that my proposed test may indeed be useful

If we could do a detailed test on [say] Zeiss, and document the performance of their telan, then it should be reasonably trivial to “invert” those results and understand what characteristics must deliberately have been left uncorrected in the objectives.

It is well-documented that Zeiss matches the compensation requirements across a wide range of objectives ... originally to be compensated by the Kpl eyepieces [160mm finite] and now by the tube-lens [ICS]

MichaelG.

.
.

P.S. __ You will obviously be aware of this, but I think it worth referencing two items for the benefit of newcomers:
Eyepieces compensating for lateral chromatic aberration are known as compensating eyepieces. To facilitate the use of our microscopes, we have computed all our objectives so that the chromatic difference of magnification in the real intermediate image they produce is always the same. We can therefore be content to supply compensating eyepieces which make up for this degree of lateral chromatic aberration. This matching of objective and eyepiece correction, introduced in the interests of our customers, is the reason why we have to warn our customers against using eyepieces of other manufacture with our objectives.

[from p35 of ‘Optical Systems for the Microscope‘ and relating to the Kpl eyepieces]
Residual lateral chromatic aberration in infinity objectives can be easily compensated by careful tube lens design, but some manufacturers, including Nikon, choose to correct for spherical and chromatic aberrations in the objective lens itself. This is possible because of the development of proprietary new glass formulas that have extremely low dispersions. Still other manufacturers (notably, Zeiss ICS systems) utilize a combination of corrections in both the tube lens and objectives.

[from https://www.microscopyu.com/microscopy- ... al-systems]
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Re: Evaluating potential microscope objective upgrades.

#19 Post by apochronaut » Thu May 21, 2020 2:21 pm

All good additions to the discussion, Michael.

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Re: Evaluating potential microscope objective upgrades.

#20 Post by Scarodactyl » Thu May 21, 2020 4:39 pm

I've only seen one attempt to quantify corrections, which (while a bit minor in scope) seemed to jive with my limited personal experience and general reputations. For those who haven't seen it (it's in German): https://www.mikroskopie-forum.de/index. ... c=22303.30
Image
Alas, all of these are finite, but the results are really interesting.
It seems like of the options measured Zeiss is the most correcting, Olympus the least, with Leitz in between and Nikon way at the bottom (but still with a slope!) I would love to see tests like this done with tube lenses too, though I suspect the logistics would be more difficult for a lens that has to focus to infinity.

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Re: Evaluating potential microscope objective upgrades.

#21 Post by PeteM » Thu May 21, 2020 5:03 pm

Stephen - any translation / explanation from German of the x & Y axis labels? Just as a visual, it does seem to confirm that Leitz and Olympus aren't all that far off - at least for visual vs. photo observation.

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Re: Evaluating potential microscope objective upgrades.

#22 Post by wporter » Thu May 21, 2020 5:57 pm

I'm not Stephen, but the translation might be:

x-axis: distance from the optical axis, mm

y-axis: % chromatic aberration in the intermediate image with 20mm

Graph title: Presentation of the different chromatic aberration corrections

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Re: Evaluating potential microscope objective upgrades.

#23 Post by PeteM » Thu May 21, 2020 6:30 pm

Thanks, Bill.

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Re: Evaluating potential microscope objective upgrades.

#24 Post by fero » Mon Nov 29, 2021 4:13 pm

If this si true:
x-axis: distance from the optical axis, mm

y-axis: % chromatic aberration in the intermediate image with 20mm

Graph title: Presentation of the different chromatic aberration corrections

than I read it opposite:
Nikon best, then Olympus and then Zeiss

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Re: Evaluating potential microscope objective upgrades.

#25 Post by Scarodactyl » Mon Nov 29, 2021 4:26 pm

It's not a measurement of quality, but of how much correction is done in the eyepieces. This is done by measuring how much ca these objectives show without vorrective eyepieces, since with the eyepieces these are well corrected. Of thr objectives measured the nikon is the weakest, since it's just an achromat. The others would be close to flat with their appropriate ryepieces, but the nikon won't get pretty much any help from that.
Ideally they'd all be apochromats for this kind of measurement but apparently it was an annoying and time consuming project to measure an objective this way.

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