Oil immersion objective on old microscope?

[75RR]

I am wondering whether it is possible to retrofit a microscope such as mine with a phase contrast objective and a opaque sheet in the filter holder, similar to the kits available for darkfield microscopy?

It would be best to locate the original Karl Kaps Phase condenser if possible.

Failing that, here is a link to an article on the subject in the very useful Micscape site:
http://www.microscopy-uk.org.uk/mag/ind ... hase2.html

[apochronaut]

Using phase objectives for brightfield is acceptable but only just acceptable. If you only have a phase set of objectives, then there isn't much choice but a quick comparison between a phase objective and the same objective without the phase ring will show a noticeable loss of contrast and a slight but noticeable loss of N.A., when a phase objective is used for brightfield. The overall effect is that of the objective seeming slightly clouded and for the best images, it is advisable to use a dedicated bright field objective for uses other than phase.
The difference becomes more noticeable with an increase in N.A.

[zzffnn]

Using phase objectives for brightfield is acceptable but only just acceptable. If you only have a phase set of objectives, then there isn't much choice but a quick comparison between a phase objective and the same objective without the phase ring will show a noticeable loss of contrast and a slight but noticeable loss of N.A., when a phase objective is used for brightfield. The overall effect is that of the objective seeming slightly clouded and for the best images, it is advisable to use a dedicated bright field objective for uses other than phase.
The difference becomes more noticeable with an increase in N.A.

I agree. And I have seen visible difference. Under oblique illumination (Heine COL on diatoms), phase apo objectives would add slight funny brownish hazy colors - not a lot, but visible when compared to a brightfield apo version.

If you think about it, if there is no difference, companies like Nikon would not bother to to make DLL (dark phase low low) objectives, as compromise, for phase and brightfield use. Nikon's other phase objectives, such as the DM version (dark phase medium), is not recommended for brightfield. Not that you cannot use them that way, they are just not optimal for that purpose.

[apochronaut]

Yes, with uses other than conventional bright field the phase ring can really cause objectionable effects.

[MicroBob]

Your objectives probably are made by Seibert. Seibert used to make high quality microscopes with apochromatic objectives and high class stands. They started to make microscopes somewhen it the 19th century but stopped probably between 1915 and 1930. From then on they specialized in supplying microscope optics to many microscope makers on the market and on other optics. They also worked for Leitz when additional capacity was needed there. In the 1970s and 1980s they supplied most smaller makers of microscopes in Germany and the rest of western Europe. The company was located in Wetzlar, where in the neighbourhood of Leitz many smaller optical companiers where located. Names like Hertel&Reuss, Will, P.Wächter and Kaps come to my mind. Microscopes from Wetzlar where usually made in Leitz style, so 170tube length/37objective length/18placing of image in the tube. Seibert supplied whatever was wanted, Leitz-style or Zeiss-style or whatever.
The company was given up round about 20 years ago. Their company buildings were to small to compete further on and moving the company was too expensive.
On german ebay the seller "Himmelsbeobachter" occasionally sells stuff from the closedown of the seibert factory. He was a friend of the family, did some work for them and has lots of boxes with optical parts and machine tools in his basement. I had a long telephone conversation with him acouple of years ago - very interesting.

Evan - the pictures you posted look good. Generally the overall appearance of the image gets worse when you switch to higher magnifications. By careful and knowledgable adjustments of the instrument some of this lost image quality can be regained.
The blue filter also blocks IR rays which are not so good for the eyes.

[billbillt]

Thanks for this very interesting post about the history of some of the German makers...

BillT

[apochronaut]

That is great information. You can tell from the barrels, that there was some optical maker common to a number of smaller companies. I guess Hacker would be in there too but what about Rolyn and CBS?

[Even]

Your objectives probably are made by Seibert. Seibert used to make high quality microscopes with apochromatic objectives and high class stands. They started to make microscopes somewhen it the 19th century but stopped probably between 1915 and 1930. From then on they specialized in supplying microscope optics to many microscope makers on the market and on other optics. They also worked for Leitz when additional capacity was needed there. In the 1970s and 1980s they supplied most smaller makers of microscopes in Germany and the rest of western Europe. The company was located in Wetzlar, where in the neighbourhood of Leitz many smaller optical companiers where located. Names like Hertel&Reuss, Will, P.Wächter and Kaps come to my mind. Microscopes from Wetzlar where usually made in Leitz style, so 170tube length/37objective length/18placing of image in the tube. Seibert supplied whatever was wanted, Leitz-style or Zeiss-style or whatever.
The company was given up round about 20 years ago. Their company buildings were to small to compete further on and moving the company was too expensive.
On german ebay the seller "Himmelsbeobachter" occasionally sells stuff from the closedown of the seibert factory. He was a friend of the family, did some work for them and has lots of boxes with optical parts and machine tools in his basement. I had a long telephone conversation with him acouple of years ago - very interesting.

That is really interesting to read. When contacting Kaps i got this link: http://www.mikroskopservice.joerghammer.de/ for questions regarding Karl Kaps microscopes. Based on your story I am wondering whether Jörg Hammer had some connection to the Seibert company.