Zeiss Condenser with polarised phase rings

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StandardX
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Joined: Wed Jan 29, 2020 9:24 am
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Zeiss Condenser with polarised phase rings

#1 Post by StandardX » Thu Feb 25, 2021 2:12 pm

Greetings to all.
I recently acquired an old Zeiss Photomic II stand - still with a few useful bits attached.
I've just taken the condenser off to take a better look - and it's not something I have seen before..... It looks likes the normal, older type multi position condenser - the type, with achr. apl. 1.4 screw on top lens - and with metal rather than plastic cover. Its a bit tatty, but all working and with good optics - so I'm pleased about that!
It has the "normal" J - Bright field, a D - Darkfield and Phase positions 2 & 3 - the numbers on the dial appear off-white in colour and the phase annuli are mirrored underneath and jet black on top - like other phase condensers I have.
It then has two further positions, also labelled 2 & 3 - but this time in a what appears to be (grubby) light blue. The phase annuli in these are not black - but transparent with a silvery mirrored appearance. On first trial on a WL with phase objectives, it gave not phase contrast, but bright field. Only when I swung in a polariser did I realise that the annuli of the light blue positions are polarised, thus on rotation of the sub-stage polariser the phase contrast effect moved between fully active to normal brightfield - with the intermediate effect being "interesting", but not great (when looking at diatoms).
This appears to be a factory-fitted - the numbers are etched in - but I cannot find anything in the Zeiss literature referring to this. I would therefore be most grateful if anyone can tell me more and suggest what the benefits might be, if any.
With thanks,
Ben
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Zeiss Standards & WL: Wild M3Z & M5: Zeiss Tessovar

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75RR
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Re: Zeiss Condenser with polarised phase rings

#2 Post by 75RR » Thu Feb 25, 2021 4:40 pm

From page 91 of the Zeiss Optical Systems Brochure
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StandardX
Posts: 6
Joined: Wed Jan 29, 2020 9:24 am
Location: UK

Re: Zeiss Condenser with polarised phase rings

#3 Post by StandardX » Thu Feb 25, 2021 4:59 pm

Many thanks for the reply - that solves that little mystery for me!

Much appreciated

Ben
Zeiss Standards & WL: Wild M3Z & M5: Zeiss Tessovar

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