What Zeiss phototube to use for high-NA Lomo objectives?

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Lou Jost
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What Zeiss phototube to use for high-NA Lomo objectives?

Post by Lou Jost »

I do a lot of imaging of live plant parts under water. I'd like to improve on my current best water-dipping objective, which has an NA of 0.50. There are some cheap Lomo water immersion objectives I could buy, but these need CA-correcting eyepieces when used for viewing. If I want to use them for direct projection photography on a FF sensor, does anyone know what phototube or intermediate lens should be used? Hopefully something cheap on eBay? Most seem to be c-mount, which would not work.

Thanks in advance!

Ichthyophthirius
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Joined: Thu Mar 07, 2013 5:24 am

Post by Ichthyophthirius »

Hi Lou,

Lomo has the same CA correction as Zeiss West and Zeiss Jena (high NA, plan and apo objectives only for Lomo and Jena). The eyepiece parfocal lengths are 10 mm (West), 13 mm (Jena) and about 12.5 mm (Lomo).

Direct projection (= objective only, no eyepiece) is not an option.

Projection with a projective (= objective + projective, 160 mm tube length) is available from Jena. It's part of the mf camera system.

The following projectives might be of interest for you:
MF-Projektiv K 2,5:1
MF-Projektiv K 3,2:1
MF-Projektiv K 4:1

Notice the "K" for compensating projective. Optical camera length is 125 mm. All you need to do is position the sensor approximately 150 mm above the projective and you get the rated magnification (no additional relay lens is required). To mount the camera, you can use the Jena mf system or a DIY setup. Projectives 3,2 and 4 have a higher magnification but they are still of interest for you because they are cheaper and the Lomo water immersion objectives are a strong field curvature.

There is a bit of explanation here https://www.mikroskopie-forum.de/index. ... ic=19729.0 and here http://www.geocities.ws/dushang2000/Mic ... hment.html (see links 7 and 8 for more information).

Personally, I would go for an afocal approach (objective + compensating eyepiece + camera lens) as that setup is more compact.

Regards, Ichty

Lou Jost
Posts: 4722
Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

Post by Lou Jost »

Thanks Ichthy, I used the wrong term, I meant "projection with CA correcting optics". I'll read your links and look for those projectives you mentioned. Very helpful!

I want to stay away from afocal set-ups wih these objectives, because all my other objectives use direct projection or tube lenses.

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