Comparison of the tiny scopes

[BramHuntingNematodes]

I was finally able to acquire a very nice Model R example for a song, and so I can post some pictures of its quality.


This is using a Nikon CF Plan Apo 10x on a full frame B&L Dynazoom with an Optem 50% reduction lens and a Pi HQ camera. The Dynazoom is outfitted with a B&L achromat condenser at NA=1.4 here adjusted as per Kohler, tamped down a bit and with the two auxiliary lenses inserted for full field coverage. The lens itself has NA=.40. This is about as good as my setup right now gets. The subject is a solitary oak leaf miner. I will use the same camera and reduction lens for all the scope images.



For later comparisons, this is the Dyna with the condenser racked down about as far as it can go, throttling the NA considerably.



So up we have the B&L model R on the left. It's a little smaller than a Coke can and dates maybe from the 30s. The case decoration is the oldest fashioned I've seen on one of these. This was considered a high-end amateur or even proto "pro-sumer," being expensive when it came out. The Selsi on the right is a relabeled Japanese scope maybe made by Carton? from the fifties or sixties, a shade more on the toy side of things. I have claimed that the R is not a toy but could be employed as a field scope. Its certainly smaller than a toy.



Here is the R. The Model R lacks a condenser and depends on the parabolic mirror for its light. It also features a continuously variable, non-parfocal zoom which allows it to vary between about 150X to 300X. This is closer to the 150x. Looks like the NA is a bit restricted, but there is very little CA all things considered.


I was thinking that maybe the condenser was a bottleneck in the imaging, so I set up a horizontal optical bench and strapped the typical 1.4 Abbe to it. I was able to image a needle in front of the field iris so it's in the right place!


I can't sense much of an improvement. Maybe marginal.



Here is the Selsi scope. For a toy, this looks not so bad! The CA is much more noticeable, and the resolution is much inferior. It does image, though. The Selsi has a single convex lens as a condenser, permanently mounted under the stage. In place of an iris it has a carousel of differently sized diaphragms you can spin around.



The Selsi also has some other lenses. Here is the 40x, which I guess provides a little more detail.



The 50x is junk unless... is it supposed to be an immersion lens? Probably not as there would be no good way to clean the stage. I guess it's just a bad lens.

So there you have it-- the R has somewhat inferior optics to top of the line lenses from 50-60 years into the future, but it still looks pretty darn decent. I wouldn't be ashamed to take it on vacation in case I found an interesting bug.

[Hobbyst46]

A very nice and informative demonstration.

For a toy, this is not bad - but, for a beginner child, it is unacceptably bad IMHO. Would drive the young person away from microscopy, rather than attract him/her to microscopy.
It is particularly interesting because there are still new small toy microscopes on the market, wrapped in cardboard cellophane packages.

Just curious - how would an achromat objective perform vs the Planapo on the same R (or Dynazoom) ?

[Javier]

Thanks for this great comparison. I find it very interesting.

For a toy, this is not bad - but, for a beginner child, it is unacceptably bad IMHO. Would drive the young person away from microscopy, rather than attract him/her to microscopy.

+ 1

[apochronaut]

Very good and interesting assessment. Thanks for taking the time to set that up.
It seems that where condensers are included with the toy/hobby scopes it is to increase illimination for those absurdly squinty high magnifications that some of them aspire to. Most of the objectives work at pretty low N.A.s. I came across one once, also made by Carton, that actually had the N.A. stamped on the objectives. 5X .06, 12X .16, 20X .35 and 45X .40, so the demands of the condenser are not great and it's clear that the high power objective can't even hold it's own with a 10X eyepiece let alone a 15 or 20X.

I think the R was a descendent of the Little Gem, which featured only one focusing knob working a rack and pinion. For those who don't know, that one was a little consumer microscope marketed as a household microscope. At one time the packing box had a picture of a louse on it I think. The Little Gem was also only about 7" tall and featured a stacked objective : three lenses that screwed one on top of each other for 1, 2 or 300X. I am not sure if there was an attempt in the assembly to obtain any level of achromatism.

Microscopes like a your Selsi also used types of stacked objectives, made up of single chip lenses and spacers, dropped into a sized barrel with an aperture in the bottom : all tightened down with a set ring, each lens magnifying by a factor. I don't know if there was an attempt to alternate flint and crown glass lenses but if so any disassembly for cleaning would require precise reassembly. More likely they were made from selected fragments of recycled pop bottles. With the more top of the line examples there was an improvement in the N.A. and achromatism of the high magnification objective by using a precision fitted front sometimes doublet lens. Those ones had some degree of achromatism. In such cases, the high magnification objective, for instance the 60X will be as sharp and bright as the 45X and with less chromatic aberration. Very often though an inquisitive owner has tried out the immersion principle and more often than not suffered a leak onto the back of the front lens, resulting in a downturn in performance.

[AntoniScott]

Interesting post. Many inexpensive "entry level" microscopes were available from Japan to microscope enthusiasts with limited financial resources in the mid to late 1950's . Some models delivered decent optical quality even at the higher magnifications although they did suffer somewhat in color correction. My interest revolved around the entry level microscopes available from Lafayette Radio and Electronics.

[MicroBob]

Interesting comparison!
Which light source did you use with the R and condenser setup?

[BramHuntingNematodes]

It is a Nikon universal illuminator fitted with a quality single led at about 4 watts, adjustable with voltage dimming. I like the little Nikon lamps and have two of them, both fitted with LEDs. They are equipped with a field iris and have a large collector lens on a helicoid focuser.

[essence25]

Can we see some close-ups of this LED illuminator?