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New objectives for old scopes...why does it have to be hard?

 
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benjamind2014



Joined: 18 Oct 2014
Posts: 216

PostPosted: Fri Dec 26, 2014 6:29 pm    Post subject: New objectives for old scopes...why does it have to be hard? Reply with quote

Well, I'm glad I read a recent article on Microscopy-UK website.

They mentioned objectives, new infinity objectives, Chinese objectives all at comparable price ranges (ranging from excellent to poor - sad) and a few other things.

I can't understand "brand compliance"... in this day and age if I ever see any company do this, especially if they have expensive objectives, I immediately abandon them.

If the scope is a DIN standard, tube length is 160mm, and the condenser is exactly the same, barring anything catastrophic, objectives that are specified for DIN at 160mm tube length with the same parfocal length should be compatible!

This sort of thing really makes we want to abandon the hobby. If I can't find something that will work reasonably well without having to cut out and sell my kidneys, I would be most appreciative.

It really doesn't look like there is anything out there - barring winning some eBay or other used marketplace lottery.

I've seriously gone through dozens and dozens of microscopes on eBay, used marketplaces, and ones that are brand new...and I'm wondering when the madness will ever stop.

Paralysis by analysis...that's what I'm struck down with, and I am suffering terribly from it.

Can anyone throw me a line here? Surely something has to make sense here...it's so confusing it's making my head spin.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 873

PostPosted: Fri Dec 26, 2014 7:12 pm    Post subject: Reply with quote

Welcome to the rant book!

Could you be more specific about what you want to know? Is it about brand complience in 160mm optics or in infinity optics?

There are different levels of compatibility among the different components in 160mm optics (objectives, eyepieces) - what specifically are you looking for?

The compatibility among infinity optics is even lower (there are good reasons for that) - what specifically are do you want to know?

Regards, Ichthy
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benjamind2014



Joined: 18 Oct 2014
Posts: 216

PostPosted: Fri Dec 26, 2014 8:08 pm    Post subject: Reply with quote

Ichthy,

I'm basically sticking to 160mm objectives for the time being, since I'm interested in buying a used microscope in Oz.

What objectives would work with a used Kyowa Microlux 72 microscope with standard non-compensating eyepieces?

What objectives would work with an old 1960s olympus monocular (it's a grey color, with a lamp and some existing lenses) with non-compensating eyepieces? Do the objectives on the old 1960s olympus scopes require compensating eyepieces?

I want to do photomicrography, so I assume replacing the eyepiece means that any objectives that require additional correction at the eyepiece would not give me a good photo. Am I correct in assuming that?
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Charles Krebs



Joined: 01 Aug 2006
Posts: 5805
Location: Issaquah, WA USA

PostPosted: Sat Dec 27, 2014 12:45 am    Post subject: Reply with quote

It is very likely that the Kyowa Microlux72 and a '60's Olympus will use objectives that have a 36mm parfocal distance.

The "DIN" standard of 45mm parfocal (in DIN 58887) was only established, I think, in 1982. (and even then nothing really forced manufacturers to adopt that). Both of the microscopes you mention are well before that time. At that time there were some 45mm parfocal objectives, but many manufacturers used different distances. Some examples:
Zeiss Jena... 33mm
Lomo ... 33mm
American Optical ... 34mm
Olympus ( 1950's & 60's)... 36mm
Wild, Reichert, Leitz... 37mm (I think 37mm may actually have been an earlier "DIN" spec)

In some cases a microscope stand designed to be used with 45mm parfocal objectives will not move the stage close enough to focus with 36mm parfocal objectives. This I have personally experienced. So I suppose it is also possible that a microscope stand designed to be used with 36mm parfocal objectives may not be able to move the stage down far enough to focus with 45mm parfocal objectives... but I don't know for sure. What I do know for sure is that even if the stand can accommodate both types, it is a real pain to work with different parfocal objectives on the same nosepiece.

My recommendation would be to look for a stand that can use 160mm tube length , 45mm parfocal objectives. If possible, try to put together a set of Nikon CF objectives. This provides more options for the camera connection optics since you are free from chromatic correction concerns. You can put the lower powers directly on a bellows or extensions tubes and use them for "macro" work. In many cases you will find that new Chinese 160mm, 45mm parfocal objectives do not require compensating eyepieces, so you could choose from that pool of objectives as well if desired. But it should not be too hard to put together a nice set of Nikon CF Plan Achromats or even an Apo or two. These would almost certainly provide better image quality than new Chinese made optics. (Unfortunately current production of 160mm finite optics is solely from China or India. Definitive info on chromatic correction from the Chinese manufacturers does not exist; and of course the optical quality of these objectives is all over the place).
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benjamind2014



Joined: 18 Oct 2014
Posts: 216

PostPosted: Sat Dec 27, 2014 4:25 am    Post subject: Reply with quote

Wish I'd known about those earlier this year...would have bought a nice brand spanking new Nikon Ci-L for less than $5k...complete with trinoc head and top line planachromats...

...hindsight oh hindsight

But right now I'll look into them.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 873

PostPosted: Sat Dec 27, 2014 4:51 am    Post subject: Reply with quote

benjamind2014 wrote:
What objectives would work with an old 1960s olympus monocular (it's a grey color, with a lamp and some existing lenses) with non-compensating eyepieces? Do the objectives on the old 1960s olympus scopes require compensating eyepieces?


Hi,

Just to explain this a bit historically. Originally, up to the 1950s, each objective had a different CDM http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artfeb02/tccdm.html (depending on the construction and the focal length).

All apochromats, and achromats of high magnification, had a high CDM (0.6 % to 2 %) and required compensating eyepieces. Low magnification achromats had a low CDM and did not require compensation. This meant that the user needed to have at least two kinds of eyepieces to use all the objectives on a microscope.

In the 1950s, Zeiss decided to build in additional CDM into the low magnification achromats so all their objectives could all be used with one kind of (compensating) eyepiece.

Other manufacturers maintained the division between compensating- and non-compensating eyepieces for much longer. For example, the short barrel (?36.65 mm) Olympus objectives you're interested in used a variety of eyepieces. You can read about this (and identify the objectives you want on Ebay auctions) with the help of the images here: http://www.alanwood.net/downloads/olympus-micro-optics.pdf

The short barrel Olympus objectives are not very expensive compared with other manufacturers and compared with Olympus LB (long barrel, 45 mm parfocal distance) objectives. So it's not advisable to mix them with other objectives as those either have different CDM, different parfocal length (see Charles' list above) or different parfocal length of the eyepieces (old Olympus eyepieces have either 13 mm or 16 mm parfocal length [I found both referenced], but not the DIN distance of 10 mm)

The parfocal length of old, pre-DIN, eyepieces can vary widely, between 5 mm (Zeiss-Winkel) and 20 mm (Vickers). This adds another layer of complexity to mixing objectives. For a beginner, I would recommend to simply stick to one manufacturer to ensure compatibility.

Regards, Ichthy
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 873

PostPosted: Sat Dec 27, 2014 5:08 am    Post subject: Reply with quote

Maybe we can give you some recommendations of stands and objectves that would be suitable for what you want to do.

At the moment the purpose and your budget aren't clear. Do you want to get a monocular microscope working on a shoestring budget or do you have $5000 to spend?

The other thing is that you shouldn't focus too much on the equipment. Developing your microscopy skills is much more important. With the right sample preparation and photography skills you can get even afordable equipment to work: www.photomacrography.net/forum/viewtopic.php?t=25177 Only when you have perfected your skills will "better" gear start to make a difference.

I don't think you really need more than 3-4 Objectives (4, 10, 20/25, 40) and a suitable eyepiece to start.

Ichthy
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phil m



Joined: 10 Aug 2014
Posts: 162

PostPosted: Fri Jan 02, 2015 1:40 pm    Post subject: Reply with quote

Ichthyophthirius wrote:
benjamind2014 wrote:
What objectives would work with an old 1960s olympus monocular (it's a grey color, with a lamp and some existing lenses) with non-compensating eyepieces? Do the objectives on the old 1960s olympus scopes require compensating eyepieces?


Hi,

Just to explain this a bit historically. Originally, up to the 1950s, each objective had a different CDM http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artfeb02/tccdm.html (depending on the construction and the focal length).

All apochromats, and achromats of high magnification, had a high CDM (0.6 % to 2 %) and required compensating eyepieces. Low magnification achromats had a low CDM and did not require compensation. This meant that the user needed to have at least two kinds of eyepieces to use all the objectives on a microscope.

In the 1950s, Zeiss decided to build in additional CDM into the low magnification achromats so all their objectives could all be used with one kind of (compensating) eyepiece.

Other manufacturers maintained the division between compensating- and non-compensating eyepieces for much longer. For example, the short barrel (?36.65 mm) Olympus objectives you're interested in used a variety of eyepieces. You can read about this (and identify the objectives you want on Ebay auctions) with the help of the images here: http://www.alanwood.net/downloads/olympus-micro-optics.pdf

The short barrel Olympus objectives are not very expensive compared with other manufacturers and compared with Olympus LB (long barrel, 45 mm parfocal distance) objectives. So it's not advisable to mix them with other objectives as those either have different CDM, different parfocal length (see Charles' list above) or different parfocal length of the eyepieces (old Olympus eyepieces have either 13 mm or 16 mm parfocal length [I found both referenced], but not the DIN distance of 10 mm)

The parfocal length of old, pre-DIN, eyepieces can vary widely, between 5 mm (Zeiss-Winkel) and 20 mm (Vickers). This adds another layer of complexity to mixing objectives. For a beginner, I would recommend to simply stick to one manufacturer to ensure compatibility.

Regards, Ichthy


It has to understood though, that there are two types of compensating eyepieces. The letter K or letters KPL on many European eyepieces , are used to designate an attempt to compensate for curvature of field, as in : plan compensating. The American makers A/O and Bausch&Lomb used the term compens or compensating to denote compensation for the overcorrection of chromatic and spherical aberrations built into their apochromats. These eyepieces also partially compensated for curvature of field and spherical aberration, when used with standard achromats and so generally they improve the performance of those objectives too. I have seen this on Cooke-Baker as well.
The calculations for the over, under correction are slightly different for each manufacturer. For instance, even though Spencer( A/O) apochromats and B&L apochromats from the 1940's , are both 160mm objectives and the eyepieces seem very similar, the compens eyepieces from each cause distortion as you head towards the perimeter of the field, when used with the other's objectives.
Mixing various brands of eyepieces and objectives, when your purpose is to obtain flat, perfectly corrected fields is risky at best because even very small deviations from the perfect formula will result in an image that can be anywhere from slightly poor to dreadfull.
Many people are used to degrees of chroma and curvature in their microscope images due to average optics or mismatched optics and think that this is common and normal. It is for many microscopes fitted with standard achromats and standard huygens eyepieces but the fact is, that perfectly matched sets of apochromats and compens eyepieces that worked over the full objective range from 10x to 125x have been in existence since about 1900 and produced images as free of chromatic, spherical and curvature defects as the glass formulas of the day allowed. The key is to not relent from matching optics perfectly and often older sets of apos or fluorites and compens eyepieces can be found for the same price or less, than a set of plain ,relatively modern achros. As well, the eyepieces that AO and B&L started selling around 1960 and other makers a little later, are multi element designs utilizing glass formulas previously unheard of, so many of those work well as compensating eyepieces with their respective apochromatic objectives. The benefit, is an increased field of view, although the central resolution of the compens oculars might be ever so slightly better.The compens 10x for instance made to match the AO apochromats between about 1915 and 1960 offered only about a 14mm f.o.v., whereas the cat.# 176 10x W.F. eyepiece released about 1960 offers a respectable 19mm.
General rule of thumb is :for basic optics you can fiddle around, the cost is low and the chance of a blunder low too . For high end stuff, unless you know from experience; always match.The aforementioned Cooke-Baker compens eyepieces for instance, work well with A/O apochromats. However, A/O and Cooke-Baker had a working relationship from the late 40's on, a little, so that may have been the reason for such compatability. Another example, again with A/O is that the infinity corrected optics that they pioneered in the late 50's became the same for C. Reichert. Thus A/O and Reichert infinity corrected objectives and their compatible oculars are fully interchangeable-----to the point that the Reichert Diavar II was fitted with A/O planachromats as standard equipment and the Reichert(U.S.A.) MIcrostar IV series was available with the same Reichert plan fluorites found on the Univar, Polyvar and Polylite.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 873

PostPosted: Sun Jan 04, 2015 12:49 pm    Post subject: Reply with quote

phil m wrote:

It has to understood though, that there are two types of compensating eyepieces. The letter K or letters KPL on many European eyepieces , are used to designate an attempt to compensate for curvature of field, as in : plan compensating. The American makers A/O and Bausch&Lomb used the term compens or compensating to denote compensation for the overcorrection of chromatic and spherical aberrations built into their apochromats. These eyepieces also partially compensated for curvature of field and spherical aberration, when used with standard achromats and so generally they improve the performance of those objectives too. I have seen this on Cooke-Baker as well.


Hi Phil,

That's very interesting. I'd be interested if you have a few references so I can read more about the US makers.

Zeiss West made "Kpl" eyepieces (ca. 1950-90) which are compensating plan eyepieces; they compensate the CDM and are plan eyepieces but they do not compensate field curvature. The "plan" designates that the eyepieces do not add additional curvature to the image (simpler designs did add additional curvature). Zeiss plan objectives produced a flat intermediate image up to field numbers of more than 25. Zeiss' microscope developer Michel (Die Mikrophotographie, 2nd ed, 1962) stated that categorically.

Earlier, Zeiss had Homals (negative, compensating) eyepieces for photography that partially compensated for field curvature in Zeiss apochromats. However, there were different Homals for different magnifications as field curvature varied with the focal length of the objectives.

According to Michel it is difficult to use visual eyepieces for correcting field curvature at all (although the book is vague in stating whether Leitz Periplan and Winkel Complan eyepieces did so to some degree); it was definitely not possible to do so across the full range of magnifications with just one eyepiece.

Loveland (1970) Photomicrography showed data from Foster ( The correlation of microscope objectives and eyepieces. J. Biol. Photogr. Assoc. 2, 140-150 (1934)) that showed the different CDM for achromats and apochromats of the time (1930s) that made the use of different eyepieces on one microscope necessary. Zeiss made the full use of the entire range (simple achromats to high magnification plan-apos) possible with just one kind of eyepiece (Kpl) available in the 1950s. It would be interesting to know if there was a company that did so earlier (as they didn't have high magnification plan objectives, one eyepieces for both achromats and apos).

Kind regards, Ichthy
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phil m



Joined: 10 Aug 2014
Posts: 162

PostPosted: Tue Jan 06, 2015 11:38 am    Post subject: Reply with quote

I have some literature but it is in quite a bit of disarray, due to a fire about 4 years ago at our farm. I will take some time and look, over the next few months. Here, at the other house I do have some catalogues, specifically from Spencer and Spencer-A/O , going back to 1895. There was a concentration of optical enterprises around the eastern Great Lakes, likely due to the natural presence of types of fine sand , as a result of glacial outwash, after the last ice age. Even Leica established a lens factory in Midland Ontario , on the eastern shore of Lake Huron, for a while. Early on, Spencer also began using natural fluorite and had demonstrated the development of superior objective lenses, capable of resolving previously unresolvable diatoms.
In the Spencer catalogues of 1917 and 1929 it is claimed that the chromatic difference in magnification is corrected for in the apochromatic objective/compensating ocular combinations offered. There is mention that the 16mm and 8mm objectives are specially corrected for flatness of field and are therefore specifically valuable for microphotography.
The compensating ocular range is 1.5x,5x,10x,10x high eyepoint,15x, 20x,25x and 30x and there is mention that the 16mm and 8mm objectives provide superior flatness of field , "even with the lowest power oculars".
Spencer also offered in addition to the standard huygenian oculars a type they called Planoscopic, which were claimed to provide a flatter and more corrected image , when used with achromatic objectives. It is further noted that the compensating oculars provide better chromatic and spherical correction when used with achromatic objectives of high n.a. There is nothing to indicate that the lower power apochromats suffered from any chromatic defects, as a result of the compensating oculars being corrected for the characteristics inherent to the higher magnification objectives, yet the mention that they assisted the correction for " the higher n.a. achromats" only, might lead to the conclusion that the lower power apochromats could have been designed to include additional CDM and so were perfectly corrected when used with the range of compens oculars.
I have used a broad range of both Spencer and B&L objective/eyepiece combinations. I have not noticed any specific defects with any apochromatic objective in the Spencer range ; generally the performance is very good across the range ( 16mm, 8mm, 4mm, 2mm, 1.5mm) available to me, when used with the compens oculars. I have available those of 5x, 10x, 10x HEP, 15x and 20x but then I have not used these optics for a while and was not looking specifically for small aberrations. I do know that the planarity and chromatic correction breaks down considerably with the huygens oculars. I will check this out further , in the future and if time permits and post some representative images of diatoms or an abbe test plate.
Spencer compens oculars and B&L apochromatic objectives, do not work and visa versa, despite the fact that they are both corrected for 160mm. There is just something slightly askew, especially in the case of spherical aberration. Oddly, by the mid 1970's, B&L and A/O eyepieces were virtually interchangeable, with as perfect edge to edge correction of planarity and chroma , as could be expected in the day , across a 20mm field, yet the objectives from each company were completely useless on the other's stands. A/O had, since about 1960 been infinity( their met microscopes have always been infinity corrected) , whereas B&L had adopted some design that rendered their objectives unfocusable on any stand, but their own. This might seem odd but they must have had a reason, because there was something happening in their optics. If I was told I could have only one biological microscope from , say 1980, I would choose a 100watt Balplan. The plan achromats made for that microscope were so good, that with the exception of the 50x .80 oil, they stopped making fluorite and apochromatic objectives. There was no need. I've compared them to a number of fluorite and apochromat objectives and in some cases they are better. There is almost no chromatic aberration, even in tiny spaces of only a few microns where chroma typically are a problem. Unfortunately, they can only be used either in a Balplan stand, or somehow in concert with the tube lens that rides in the yoke over the objective. Presumably, this corrects the image to the same tube length that the correcting lens in the bottom of an A/O head does, otherwise the two sets of eyepieces wouldn't be so cross-compatible.
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