Balplan 10x objectives

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
Post Reply
Message
Author
User avatar
wporter
Posts: 253
Joined: Wed Oct 21, 2015 10:18 pm
Location: USA

Balplan 10x objectives

#1 Post by wporter » Wed May 08, 2019 11:45 pm

Here are five different 10x objectives that look to be for the Balplan, the farthest left a flat-field that looks very much like the adjacent planachromat. Does someone know the difference and/or the evolution of the 10x objectives as displayed by these? I have some guesses, but it would be nice to hear from the more knowledgeable. Thanks.
Attachments
P5080018-1024x1024.jpg
P5080018-1024x1024.jpg (86.25 KiB) Viewed 811 times
P5080019-1024x1024.jpg
P5080019-1024x1024.jpg (78.82 KiB) Viewed 811 times
P5080020-1024x1024.jpg
P5080020-1024x1024.jpg (57.7 KiB) Viewed 811 times
P5080021-1024x1024.jpg
P5080021-1024x1024.jpg (73.86 KiB) Viewed 811 times

apochronaut
Posts: 2732
Joined: Fri May 15, 2015 12:15 am

Re: Balplan 10x objectives

#2 Post by apochronaut » Thu May 09, 2019 3:05 pm

Paging Harold Rosenberger. Paging Harold Rosenberger. Oh. Not available? On a River cruise of the Yangzte?

Here's what I've seen during use and in breaking some down. It's some stuff from catalogues and some observations.

Short one was introduced in '75 or '76, as a long working distance objective. It has a greater w.d. than the the 4X, 9.95mm. It is catalogue # 31-12-19 10X .25 l.w.d.. The 10X planachromat standard w.d. objective at the time had a tight w.d. for a 10X of only 1.02 mm.
You have them nicely arranged chronologically.

Left one I'm pretty sure is an early version of the planachromat, still marked flat field. There seems to have been a point in time when B & L redesigned some of the objectives but not all of them. I have 3 versions of the 20X; an older straight barreled flat field, a newer barreled flat field and a planachromat in the same barrel but painted instead of engraved, dating it to after about 1985 when all of Cambridge Instruments acquisitions went to painted barrels. I see zero difference between the 3; maybe a bit of contrast between the earliest and the latest but that is probably a matter of coating technology. They don't seem to have changed the 20X much over time. Question I have is whether you find any difference in the performance of the two 10X on the left? The earlier Dyn-optic/zoom straight barreled 10X flat field objectives, seem to be distinctly different than the later planachromats, which at the beginning were marked flat field as well. The ones first made for the Dynoptic and Dynazoom had a wider front lens, then the next flat field design had a different barrel with a narrower front lens and then a very similar objective exists as a planachromat. There is a change in performance too. In testing them, I have found the planachromat design to have better contrast and colour correction. The 10X and the 100X first generation flat fields had the weakest performance. It seems likely that they decided to improve the 10X first, changing the barrel, keeping the flat field nomenclature and going on to the 100X and 40X later at which time they made a decision to use the term planachromat. I can't say I have ever seen a 40X, 50X or 100X in the type of barrel with the overt grip ring marked flat field, except as phase versions. Have you?

The Academic was a student microscope that was also fitted with flat field objectives, normally with stage clips and dressed down versions of the flat fields with brushed aluminum housings. Those say simply flat field on them and they have pin wrench grips on the barrels so they can be turned in hard enough so that inquisitive little fingers can't undo them. The optics inside look pretty much the same as the brass barreled top of the line earlier flat field achromats which were sometimes fitted on the Academic along with a fancy mechanical stage with drop down coaxial controls. What microscope was your 10X flat field originally on?

The two right hand ones are the later planachromats with the different front lens housing and shorter barrel. One older one with engraved markings and a newer one with painted markings. Those objectives are physically shorter than the earlier planachromat objectives giving a longer w.d. The front lens looks to be the same and in the same protruded location but they have reduced the length. Perhaps there was some advice from users that having a longer W.D. and therefore better access to the slide was advisable with the 10X. Previously, the 10X was the same length as the 4 other objectives of higher magnifications and later, as a painted barrel objective the 10X went through even another incarnation with an even shorter barrel yet.
Barrel lengths of the 10X objectives from the front extremity to the shoulder are : early flat field 41mm, brushed aluminum flat field 42mm ( has a physical guard ring around front lens of about 1mm), early planachromat 43mm(again with guard ring), later planachromat 40mm, even later planachromat 37mm. ...all measured with a ruler. I don't have a l.w.d. 10X. It looks to be about 32-33mm?

User avatar
wporter
Posts: 253
Joined: Wed Oct 21, 2015 10:18 pm
Location: USA

Re: Balplan 10x objectives

#3 Post by wporter » Thu May 09, 2019 7:00 pm

Well, Harold must have fallen off the boat. I'm not sure I would want to fall into the Yangtze, these days.

Thanks for the breakdown. Comprehensive as usual.

All of the objectives pictured are parfocal. The working distances are about 1mm for the left two, 10mm for the shorty, and 2mm for the newest ones on the right.

All seem (to my decrepit eyes, and allowing for differences in condition) to have the same resolution. Maybe, as you point out, there is a slight increase in crispness, or contrast, between the older long ones and the newer long ones; nothing to write home about.

Oddly, though, the shorty exhibits a slightly smaller magnification, maybe not even 5%, just noticeable.

B&L did a fine job of maintaining resolution (as specified by the N.A.s all being 0.25) despite the increase in working distances, especially for the shorty. Which is 33mm long as you guessed.

I haven't seen any knurled flat-fields in 40x-100x, either; only on the 10x, the 4x, and the 2.5x. Did the latter two even come in PAs?

I don't recall where I got the 10x flat-field.

Thanks again for the history.

apochronaut
Posts: 2732
Joined: Fri May 15, 2015 12:15 am

Re: Balplan 10x objectives

#4 Post by apochronaut » Thu May 09, 2019 8:25 pm

or off the wagon. I never thought about that aspect of the 4 and 2.5X but come to think of it, you are correct. I have seen only flat fields. The 2.5X emerged sometime during the Balplan years and physically designed with the overt grip ring, like the planachromat series. The 4X with the overt grip ring, had a flat field predecessor made for the Dyna flat field series originally and carried forward to the Balplan. The specs. are the same 4X .09, however the older one weighs 80 gm. while the newer design weighs 56gm. The rear lens on both is the same and positioned in the rear end of the barrel at an equal height( just the coating is different) and so does the front element seem the same. They are the same length. It looks to me that they are the same objective, just packaged in a different barrel.

The transition period seems to be around the mid-70's, when they decided to call everything planachromat instead of flat field. In the spring '75 price list they had not yet completed the redo of the objectives. The 20X is notably still the older straight sided version cat.# 31-10-61, which would be a 20X .50 flat field achromat. The phase objectives are still also the older straight sided design flat field achromats 31-10-51, 52,53 and 54, as are the flat field apochromats. However , all are referred to in the actual text as plano objectives; planachromats,planapochromats and plano phase contrast. In the next price list, somewhat over a year later, the 20X has been upgraded to the newer design with a new cat.#31-12-23 but all are still called plano and the apochromats never did get a new barrel design or have planapochromat stamped on them but they are always called that in the catalogues. It seems they used the two terms interchangeably but in some cases the plan objectives were in fact unique optical designs when compared to the older flat field version, so maybe the 10X, 40X, 100X and possibly 50X objectives were revised, while the 2.5X, 4X, 20X were not. The apochromats were not and there were some apochromats and fluorites that were not brought forward to into the Balplan program, yet still work on one: 50X dry flat field fluorite, 100X oil immersion flat field fluorite, 75X oil immersion flat field apochromat, 100X oil immersion flat field apochromat and 125X oil immersion flat field apochromat are the ones I know about.
Another oddity about the catalogues is that there is a 50X .85 planachromat that shows up in 1976 sometime, discontinued by 1986. I have never seen one but I have a 50X .80 planfluorite oil and have seen another, an objective that shows up in none of the catalogues I have or have seen, yet it is a planfluorite, so probably developed after 1975 and therefore a Balplan objective.

Post Reply