LOMO & Zeiss Jena Pre-DIN Objectives.

 Correcting the stiff coverslip thickness correction collar on the LOMO 40x NA0.95 apo

Compiled by Ian Walker using material kindly contributed by Frithjof Sterrenburg.

 (Printing: Please choose your printer's 'landscape' mode to print out.)

My comment in the above article on the stiff coverslip thickness correction collar on the LOMO 40x NA0.95 apo, prompted Frithjof Sterrenburg to kindly share his suggested method of correcting this. The procedure is presented below using Frithjof's images with his permission and the author thanks him. Note that this should only be carried out for old objectives, if required. The guarantee would be invalidated on a new example and the suppliers should be contacted. This procedure is, of course, carried out at the objective owner's risk.

Frithjof remarks:
I have dismantled my 40x apo on camera and here is a DIY show with captions. Note that this is not to be attempted by the uninitiated, although it's not really difficult, it requires very clean and careful tinkering. For a final check to see whether the marking on the collar is true, adjust collar IN DARKFIELD with a slide of known coverglass thickness for optimum image quality. If the markings are off, loosen the tiny screws of the collar and adjust collar (NOT the collar ring) for correct value. Adjustment ex factory is not always 100% OK. ... A good lubricant should be used after cleaning for the coarse screw. The sliding tube is just given a TINY film of thin oil.

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