...awakening a Leitz SM microscope...

[tonikon]

Hello to all forum friends,

This is my first post and my legs are shaking a little
Some years ago, I bought a second-hand Leitz SM microscope (black enamel series) paired with Apo objectives, periplan eyepieces, Berek condenser and trinocular head. I bought it because it is a very fascinating tool (and because it was a really good occasion...), but now I want to begin to use it. Infact, I have a personal photographic project about "life in a drop of water" and I have to photograph (mostly in brightfield microscopy) a lot of living specimens.

I have spent a lot of time taking high magnification pics in reflected light (2x-20x with stacking softwares and automated macro rails), but I'm a real newbie in photography with compound microscopes.

I have already adapted a led illuminating system (a white Cree led hidden inside an old microscope illuminator) but I would like to ask you if my setup is really "competitive" with much more modern infinity microscopes in terms of image quality (risolution, optical aberrations...). Conversely, I'm not worried about speed and easiness of use. I have to spend a lot of time taking photos of a lot of specimen and I'd like to be sure to start with the right tool. I know that illuminating technics, pos-production and quality of sensors are determinant, but I'm afraid that that general optic quality of my tool should be the real limiting factor.

Moreover, it would be nice if someone can help me to add some new part (phase contrast condenser and objective, darkfield condenser...) to extend the operativity of my setup for living specimens.
In order to give more information about my setup, this is the objective list:

- Leitz SM with Trinocular head
- Berek condenser
- Periplans eyepieces (10x18 in the trinocular head)
- Leitz Apo 12.5/0.30 170/
- Leitz Apo 25/0.65 170/0.17
- Leitz Apo 40/0.95
- Leitz Apo Oel 90/1.32 170/0.17
- A fistful of Pl/NPl objectives and a Darkfield condenser (which I wasn't able to use correctly)

Forgive me for writing too much and asking too many questions and have mercy on my unsure English.

Thanks in advance,

Toni

[BramHuntingNematodes]

The field will be small but the resolution should be excellent. This is a superb microscope, and if you ever get a new one it will likely not be as sharp.

I don't find the lack of plan corrections to be overly troublesome, even in photography. This is especially true when being able focus on an organism in the center of the field rather than a broad cross-section of tissue. If it bothers you there are some stacking techniques to overcome it in software.

[tonikon]

Thank you very much, BramHuntingNematodes,
your reply is really encouraging and very helpful. The lack of field flatness is not a real problem ... I've been using stacking software for many years and shouldn't have any problems. If anything, in terms of mechanics, my Leitz does not have the classic double focusing knob but an unusual single-knob control ... a few degrees of fine focus and then again coars adjustment. This doesn't match with automated stacking solutions, but it shouldn't be a problem to work with manual focus stacking.
To connect the camera to the microscope, I have done a sort of adapter composed by four parts: a mechanical adapter to put the eyepiece on the trinocular head, a Periplan 10x18, an inverted Schneider Xenoplan 28mm f/2.0 (usually closed to f/2.8) and an adapter to m4/3 camera. The results seems adequate, but I have not enough experience to compare my results. For sure, I have not vignetting and images are sharp corner to corner.
But the real mistery, for me, is illuminating methods...every advice or suggestion here is really well accepted...
Toni

[apochronaut]

Although your collection of optics is first rate for it's time, older microscope optics can suffer from lower contrast than optics of similar specification made in the modern era. That is partially dependent on whether yours were made in the early coated optic era, which I suspect they were but it can also be caused by the quality of illumination and whether the condenser is doing an adequate job. Lens designs have improved as well.
For most BF work , I would think that your set up will be adequate with the following provisos.

Your condenser N.A. will have to be the 1.40 version in order to take full advantage of your oil apo objective. I don't know all of the design changes Leitz may have gone through in that period but your top lens is the .95 dry condenser, is it not? Apparently the 1.4 top lens is difficult to find as a separate entity.

The illumination on that model is a 15 watt tungsten, I think. This would definitely limit your ability to do high resolution DF plus the fact that your 90X objective lacks an iris diaphragm. You should be able to do it with the 40X plan .65, though. Your apo .95 objective has a correction collar but I think lacks an iris diaphragm, so D.F. is off the table likely, for it too. The condenser, if it is an oil cardioid type, is primarily designed to cover the field of 40X and up objectives, so despite the value of DF, most of your objectives are not useable. Possibly the 25X, too?
Still, 15 watt tungsten should be fine and usefull for most BF work. It will take some filtration, which always entails a loss of intensity.. Retrofitting older systems to led is alwsys possible but with the illumination optics designed for a tungsten filament lamp, you might end up worse off ; unless you know of a tested design. Most higher end transmitted microscope photography is being accomplished with filament light sources.

[tonikon]

Hi apochronaut,
you are right ... probably I can't use the 100 oil objective and waiting for the correct condenser I'll remain in the 12.5-40x range.
The original lamphouse (with its tungsten lamp) was replaced by a DIY led illuminator. I can translate the led house in order to centering it, but I haven't a real diaphragm on it. Over the lamphouse, there is a strange condenser, called Berek condenser, projected to obtain the Kohler illumination even without the iris diaphragm. It shows a two diaphragm design, and (if I have well understood) the lower ring plays the role of the field diaphragm situated on the base of most microscopes. But I really don't know the mysteries of Kohler's lighting and I grope around without knowledge ...
Toni

[BramHuntingNematodes]

For Kohler you need a field lens to collimate your LED, but not necessarily a field iris (Kohler used a cardboard stop I think?). After that your Berek will be fine, and has that additional iris that can serve as field diaphragm. It's just like any flip top condenser in its use I should think. I'm not familiar with its color correction but I should think its good.

You can use the high power objective, but without the oil screw-on top they won't have any better resolution than your 40, which is still pretty good. Probably easier to switch eyepieces when using the 40 than to oil the slide for the same effect.

I'd like to know more about your LED. I have gotten some good results with LED light after many, many experiments. Most failures.

[apochronaut]

There is some debate about the resulting effect that the use of a .95 dry condenser will have on an immersion objective capable of an N.A. above 1. Based on the abbe limit, the condenser has a total limiting effect, and does not allow the objective to achieve an N.A. above that of the condenser. However, Rayleigh refined resolution theory, including the constant 1.22 ( derived from the first diffraction pattern from zero) and the ratio between the condenser N.A. and objective N.A. which shows that the resultant resolution will be a combination of the two. For a 1.4 N.A. objective working with a .95 condenser, the resulting N.A. will be somewhere in the neighbourhood of 1.25, depending on the wavelength of light used.