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PostPosted: Mon Aug 29, 2016 11:55 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
Yes, I know they were made in Rochester but for many years I, and I'm sure I'm not the only one, have been truly buffaloed by their objectives. They don't work in any other microscope nor do other microscope objectives work in a Balplan. This isn't too much of a hardship, because in a number of comparative tests I have done with Balplan achromats in a Balplan, against other contemporary achromats in appropriate stands, the Balplan objectives have always done as well or better. I have felt for a long time that B & L was doing something different, that gave their optics in the last 20 years of their production an edge. The colour correction of the last planachromats they produced is better than some fluorites made up until the 1990's.
Digging into some patents has provided a likely answer.
Bausch & Lomb , by the 1960's, realized that the going would be tough in the future. Japan was continuously upping their quality and had a distinct advantage in the cost of production, whereas Germany had always been competitive but still had a distinct edge on production costs.
At the time, a f.o.v. of 18mm was what most companies offered as wide field in the general market. To produce wider fields, with full edge correction was very expensive and generally could not be produced in a modestly priced lab instrument.
B & L had an answer and their answer, is the reason that their objectives are specific to only a few microscope stands.
They sought to produce a wide field, fully corrected microscope that was economic, by designing all the objectives in the system to take advantage of the same rear lens pack. This corrective lens was set apart from the middle lenses of the objectives by an air space and became a tube or telon lens situated above the nosepiece. Thus, the Balplan( as well as the earlier Dynoptic/Dynazoom flat field objectives) were actually semi-obectives of low magnification. What this allowed B & L to do was produce a series of very low magnification objectives of a more complex design than normal, with very high N.A.'s. The 100X objective for instance is actually a 20X 1.25 N.A. This low magnification and high N.A. allowed for superb curvature of field control, spherical and chromatic aberration correction, prior to the 5X magnification and correction trimming provided by the remote common rear element. The relatively gentle meniscus required for such modest initial magnifications, also allowed for flatter wider fields. B & L was able to offer 22mm at a time when most companies struggled to achieve 18mm and at competitive pricing .
Over the 25 or so years that this design existed, they produced several ranges of semi-objectives. The first were flat field achromats, flat field fluorites and flat field apochromats followed eventually by much improved planachromats, that were so good that they ceased production of the flat field fluorites. There was also at least one planfluorite, a 50X .80 oil immersion.
The actual magnification of the objectives is 1/5 of the marked value but the N.A., is that, that is marked. The large relative size of the objectives allowed for very wide fields and superior correction without having to resort to very expensive glass formulations , the highly difficult grinding of extreme curvatures and more complex lens formulae.

File comment: Side view of the basic 20 watt halogen stand.
DSC01842 (1024x896).jpg
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File comment: Front view of the basic 20 watt halogen phase contrast instrument. There were many permutations, including vertical DIC, 100 watt research stands and pol
DSC01844 (575x1024).jpg
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File comment: A set of phase contrast objectives; 10X .25, 20X .50 , 40X .65 and 100X 1.25 planachromats flanked by a conventional 97X 1.30 B & L 160mm objective on the left and a couple of D.I.N. objectives on the right.
DSC01845 (1024x562).jpg
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File comment: 2.5X, 4X and 100X 1.25 iris planachromats, flanked by a conventional B & L 97X 1.3 160mm objective on the left and a Jena D.I.N. objective on the right for comparison.
DSC01846 (1024x564).jpg
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File comment: 7.5X .20 , 25X .65 , 50X .80 oil (planfluorite) , 75X 1.20 oil and 125X 1.4 oil flat field apochromats flanked by a conventional B & L 97X 1.3 160mm objective on the left and a Jena D.I.N. objective on the right for comparison.
DSC01847 (1024x562).jpg
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Last edited by apochronaut on Sun Jan 22, 2017 8:05 pm, edited 1 time in total.
PostPosted: Tue Aug 30, 2016 10:30 pm 

Joined: Fri Oct 24, 2014 1:57 pm
Posts: 3247
Interesting instrument. B&L also acquired Criterion Telescope Co. in the early 80's.

They switched to eye health products; lenses, contacts, implants, etc. Acquired in the mid 2000's.

I know this because I live in Rochester.

A little extra history :)


PostPosted: Wed Aug 31, 2016 1:47 am 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
You could be potentially inundated with the history of optical development, living in Rochester, JIm. Some of the finest innovations in optics stem from those environs.
The microscope business of B & L became a separate enterprise of the parent company, sometime in the 1960's, I think it was. It was called the Scientific Optical Products Division. Once they patented the soft contact lens: that provided the payroll of the company and the Scientific Optical Products Division a bit of a sideshow for them. They really didn't need the microscope business because based on their Opthalmic business they became a highly profitable Fortune 500 company. I think the option to sell off the Scientific Products Division to Cambridge Instruments in 1984 was a win win situation. Cambridge needed to expand their scientific optical business and B & L needed to focus on Opthalmics, which was highly lucrative.
However, they did make fine microscopes nontheless and contributed greatly to the advancement of microscope technology. Navitar and Hoffman Modulation Optics certainly carry on Rochester's enviable tradition of innovation.
Here are a couple of front and rear pictures of the B & L objectives. Oddly, they do not look like partial objectives, they look like finished objectives but the part has been brought to such a high degree of refinement that it goes unnoticed. The 75X objective, looks like a 75X objective in the pictures( as do the others look their part) but it is actually a finely corrected 15X 1.20 N.A. oil immersion flat field apochromat waiting to be coupled to a 5X remote correcting rear element in the optical tube. The resulting image quality of the combined optical system is very fine, indeed. Nobody, had better microscope imaging in it's time.....flat field, exceptional colour correction, exceptional spherical aberration correction and wonder of wonders for the mid-70's a 22mm f.o.v. in a reasonably priced lab microscope.

File comment: Balplan semi-objectives 4X( actually .8X .09) planachromat, 25X ( actually, 5X .65) flat field apochromat, 75X( actually, 15X 1.20 oil) flat field apochromat and 20X ( actually 4X .50) flat field phase achromat. Front view.
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File comment: The same as above ; rear view.
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PostPosted: Wed Aug 31, 2016 9:31 am 
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Joined: Sat Dec 26, 2015 10:33 pm
Posts: 1020
Location: Cambridge, UK
Keep them coming. We all love microscopes and learning more about them.
Many thanks.

PostPosted: Wed Aug 31, 2016 12:05 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
One other interesting design feature that Bausch & Lomb incorporated into their objectives, going back into the 40's is ease of parfocality. Objectives could have slight manufacturing differences, so parfocality although close, might not be dead on.
Each objective B & L made , has adjustable parfocality. If you look at the 4 gold flat field apochromat objectives pictured above, and as well, the older 97X 1.30 achromat to the left of the first vertical group shots, you will see a small seam, between the knurled grip ring section and the objective shroud. You will see that the gap is wider on some objectives than on others. The shroud is actually a threaded cap over the nose section of the objective. By loosening or tightening the rear diaphragm and lock ring on each objective and simultaneously loosening or tightening the shroud on it's fine thread, you can move the actual entire objective lens pack back and forth relative to the objective body, to obtain perfect parfocality between objectives.
The later objectives, such as the planachromats and planfluorite pictured, which are not designed with a shroud, have a small cam built in, actuated by a small screw, that moves the lens pack back and forth relative to the objective body, in order to get precision parfocality. You can see the mechanism clearly, in pictures 3 and 4 on the two red 100X planachromats.

Last edited by apochronaut on Sun Jan 22, 2017 8:10 pm, edited 1 time in total.

PostPosted: Wed Aug 31, 2016 6:00 pm 
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Joined: Sat Jun 20, 2015 3:57 am
Posts: 2523
Location: Houston, Texas
Thank you, Apo, for this informative thread.

Selling my Canon FD 200mm F/2.8 lens

PostPosted: Wed Aug 31, 2016 10:59 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
Thank you, Fan.

PostPosted: Tue Jul 10, 2018 3:11 pm 
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Joined: Wed Oct 21, 2015 10:18 pm
Posts: 116
Location: San Marcos CA USA
Trying to rejuvenate a Balplan, I found this thread very illuminating. Thanks to Apo for once again for giving us a brain-dump from his extensive study of objectives.

Apo, if I understand it correctly, the planachromats were the last and best of the Balplan-compatible objectives, so there is no practical sense in hunting down apochromats for the scope, unless they just drop into your lap, so to speak. Is this correct?

Below is an image of five Balplan objectives. So the PA version of the 100x is upgraded from the flat-field variety? And I see that even the 10x planachromat phase has a different barrel from the 10x non-phase planachromat; interesting.

Any comments welcome.

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PostPosted: Wed Jul 11, 2018 11:34 am 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
The first ones were for the Dynoptic and Dynazoom but only for those microscopes with
the words Flat Field printed boldly across the front of the head. I've
seen a 100x 1.30 Flat Field Fluorite, that was physically similar to the
last U.S.A. made 160mm objective series from B & L, just larger, with no
160 written on it and Flat Field clearly marked. There were most likely
achromats like that too but B & L may have had trouble with people
understanding that the Flat Field and 160mm objectives were for mutually
exclusive instruments, so the physical format of the barrels was dramatically changed early on.
The first clearly different Flat Field objectives were those with large
straight sided barrels but with a small knurled ring near the base.
Polished chrome barrels for the achromats and fluorites and polished
brass for the apochromats. For DF you have to replace the rear diaphragm
with one of smaller diameter for the high N.A. objectives.
I know of 4x .09, 10x .25, 40x .65 and 100x 1.25 oil as achromats : 50x
.80 and 100x 1.30 oil as fluorites and 7.5x .20, 12.5x .30, 25x .65, 75x
1.2 oil and 125x 1.40 oil as apochromats. I'm pretty sure there were also
40x .85 and 100x 1.30 oil apochromats as well.

Some of those Flat Field objectives were carried forward into the Balplan
> program and some were not but they are all made with the same
> corrections, so any work fine. I think what happened , is that they decided to
> upgrade the program and deleted those that either weren't in their plans
> or needed technical upgrading.
> To complicate things further, they changed the barrels into ones with a
> more convoluted shape with a large central knurled ring, yet retained the Flat Field
nomenclature. B & L has always had an internal parfocalizing adjustment,
so with the newer barrels they incorporated an internal cam,
actuated by a small screw in the side.
Some of those , mainly in lower magnifications; 10x and 20x with the newer
barrel shape can be found still marked Flat Field, while others are marked
It's possible that for some objectives they just brought some of the same
designs forward into the newer barrels and decided that Flat Field was no
longer as useful a marketing nomenclature and switched to Planachromat instead
but it seems likely that two newer style barrels exist, one as a Flat Field and
one as a Planachromat.
> I have never seen a 100x in the newer shaped barrel that is marked
> Flat Field and in tests, the 100x 1.25 oil Planachromat, is a noticeably
> better objective than an older 100x 1.25 oil Flat Field Achromat. However,
I see that you have both a Flat Field and a Planachromat in the newer barrels.
albeit , slightly different ones.
I would be interested to know your impressions of the differences in them.
> At the time that the newer barrels came out they also seem to have
> deleted the older straight sided fluorites. One re-engineered fluorite I
> know of for sure is a 50X .85 oil planfluorite in the new style barrel,
with parfocalizing cam.
> The newer planachromats are so good that they are better than the earlier
> straight sided Flat Field fluorites, displaying very little if any chroma
> in tiny, normally diffractive spaces. The 50x Planfluorite must have been
considerably inproved, in order to fit well with the Planachromats and indeed it is.
> However the reason for the deletion of the higher magnification Flat
> Field Apochromats is probably somewhat different because they are all
> excellent, displaying very fine flat field apo quality. The N.A.'s alone ,
indicate that.
The dovetail for the condenser of the Balplan is distinctly
> different from that of the Dyna series and they had not yet redesigned a
> high N.A. achromatic/ aplanatic condenser yet for the Balplan. It was
> probably left to near the end of the development list. I'm pretty sure
> that they had plans to refine the Flat Field Apochromat series originally
> for the future but by the time they had refined the bread and butter
> stuff, the entire program was in jeapardy due to new ownership and an
> entirely different consolidated stocklist. First for Cambridge
> Instruments and later the Cambridge/Wild-Leitz merger. The Balplan just
> wasn't needed. All they ever listed in the 70's catalogues as apochromats
for the Balplan were the 7.5x .20, 12.5x .30 and 25x .65 and seemingly
entirely unchanged from the objectives that were made for the Dyna series.
The pictures look identical to the objectives made for the Dyna series but
they are listed as Planapochromats. I suspect that they are the Flat Field Apochromats
> rebranded. I have never seen a Planapochromat, except in the catalogues.
All of mine ( 7.5x,25x,75x and 125x) are marked Flat Field Apochromat.
> In later literature the apochromats are not mentioned at all. They possibly did
> not sell well, due to cost; another nail in the Balplan coffin.
> Another omission in catalogues is the is the 50X .85 oil planfluorite.
I have one of those and have seen one other but it shows up in not one of the
6 trade catalogues or price lists printed between 1975 and 1986 that I have,
devoted to the Balplan. Beginning in the Oct.1 1977 price list cat.# 31-12-25,
a 50X .85 planachromat shows up but it is gone by 1986. I have not ever seen one of those.
> So, it is safe to say that the more slender design Planachromats 2.5X
> .06, 4X .09, 10X .25, 10X .25 L.W.D., 20X .50, 40X .65, 100x 1.25 oil and
> 100X 1.25 oil with iris are of superior performance, with resolution and
> contrast noticeably better than the older straight barreled Flat Field
> Achromats. I have trialled two entire sets; 4x,10x,40x and 100x against
each other and the Planachromats are superior in all ways , visually.
Presumably the 50x Planachromat oil would be as well and of course
50X .85 Planfluorite. Personally, I wouldn't bother with older Flat Field
> Fluorites( if you can find one), although for a good price, one or more
> would certainly be better than the older Achromats.
> All of the Flat Field Apochromats are worth while but scarce as scarce
> can be. I'm still in the design stages of working an achromatic high N.A.
> condenser into a Balplan housing for the 75X 1.2 and the 125X 1.4 oil
Flat Field Apochromats.

PostPosted: Thu Jul 12, 2018 12:52 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
The earliest objectives for the program referenced above, looked like this.
https://www.ebay.com/itm/MICROSCOPE-PAR ... xyx0JTiTKM

That one is a metallurgical version but the early flat field fluorite, corrected for a .18 cover, that I once had looked almost identical and was spring loaded too. Later objectives, lacked the spring loading. The telescope lens used in the instrument appears to be the same for all objectives, diascopic, episcopic and met. The epi objectives, were slightly larger, with a 25mm thread. They work in the standard nosepiece, when fitted with an adapter but they get a little long. I have an 80X .90 flat field fluorite epi, which is a really superb no cover objective.

PostPosted: Thu Jul 12, 2018 3:27 pm 

Joined: Mon Aug 21, 2017 9:02 pm
Posts: 828
Reading this very informative review I remembered to have read a statement about interchangeability some time ago on this respected forum - and found it!

apochronaut wrote:
Interchangeability, despite the fact that in theory it was promoted by the RMS and others over many years, has never really existed anyway. Leitz, and a few others never conformed obviously, and when you factor in the necessity with most 160mm systems to employ proprietary eyepieces and the differences in parfocal distance with many, it has always been a bit of a myth....The optics are outstanding. The planachromats perform like planfluorites.

I learned it the somewhat hard way: on a finite TL microscope, mixing Zeiss objectives with Olympus eyepieces, or vice versa, works fine - as long as the judge is eye vision alone. The camera demonstrates the CA problems.
The happy news is that on modern, infinity corrected microscopes, even the objective thread differs among brands, so any pretensions :oops: :? about interchangeability are spared...

Zeiss Standard GFL+Canon EOS-M10

PostPosted: Thu Jul 12, 2018 6:07 pm 
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Joined: Wed Oct 21, 2015 10:18 pm
Posts: 116
Location: San Marcos CA USA
Apo, thanks for the writeup; exhaustive as usual, and much appreciated by us objective hunters. You also bring home the chaos that must have overwhelmed the microscope industry during the last quarter of the 20th century.

As far as the two 100x objectives (the slightly different new-style barrels, one 'flat-field', the other 'planachromat' in my image above), they seem to perform pretty much the same; perhaps the planachromat is very slightly better.

Your point about needing the correct eyepieces is one that needs stressing, especially to beginners, and especially involving unusual microscope designs, such as the Balplan. The one I am fixing up came with two B&L eyepieces, marked only 10x W.F., silver with a black & brass slotted retaining ring at the top (eye lens); turned out to be very inferior to the proper eyepieces I obtained later, the kind marked 31-15-61, 10x W.F.

PostPosted: Thu Jul 12, 2018 9:32 pm 

Joined: Fri May 15, 2015 12:15 am
Posts: 2026
Thanks, Bill. In looking at your pictures, I suspect that 100X flat field achromat you have, with the more recent " slender nose design" ( I guess that is about as good as I can dub it), doesn't have the little set screw and cam mechanism with which to parfocalize it? It probably used the old B & L system of sliding the lens pack back and forth in the barrel..
I see that it has a seam near the bottom of the larger diameter section of the barrel. When that section is unthreaded slightly, you should be able to turn the rear diaphragm in with a pin spanner, circlip pliers or other device, driving the lens pack farther down in the barrel. Thus, by loosening or tightening that lower section , along with tightening or loosening the rear diaphragm, the entire lens pack can be moved up or down in the barrel relative to the nosepiece, affecting it's parfocal distance.

With the older broad, straight barrel types, that big outer shroud is loosened with ones hand, and then the rear diaphragm tightened to lower the lens pack and the reverse to raise it.
If you look at the picture of my flat field apochromats with the one older 97X 1.30 B & L 160mm tube objective on the left, the 50X .80 oil planfluorite in the middle and the D.I.N. Jena 100x 1.25 objective on the right, you can see that the seam in the middle of the objective barrels of the apochromats varies in width. That seam widens or narrows, based on how they are parfocalized. The 97X, also has a gap at the top of the shroud, next to the knurled section. That gap can be closed right tight with a certain parfocal adjustment, or even be a bit wider than it sits in the picture. On the 50X .80 planfluorite, you can just barely make out the locking screw for the parfocalizing cam, on it's left side.

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