I often see references about a Zeiss Oil condenser with ON 1.4: what is it ?
Does one have to add oil between the condenser and the glass slide ?
What is the interest ?
has anyone experience with it ?
Phil
OIL CONDENSER
Moderators: Chris S., Pau, Beatsy, rjlittlefield, ChrisR
OIL CONDENSER
Zeiss Axiophot, transmitted and Fluorescence
BK5000, Transmitted and CP
Wild M20
BK5000, Transmitted and CP
Wild M20
Without oil the maximum NA of a condenser is 0.9 (0.95 theorical).
A condenser labelled 0.9 or smaller must be used dry.
A condenser labelled >0.9 must be oiled to to the slide to reach its nominal NA, if used dry it could get 0.9 maximum. This only will matter for immersion objectives.
The need of a condenser with NA>0.9 is not so clear. In fact many top quality microscopes today use dry 0.9 condensers. In theory in brightfield for maximum resolution the condenser NA must match the objective NA, but to get enough contrast you need to close the aperture, lowering the NA about 20-30%....
I use an achromatic aplanatic 1.4 condenser and compared to a simpler 0.9 the difference is barely noticeable in most cases, and I suspect it is due to its superior optical correction. I use it oiled mainly for DIC with objectives with NA 1 to 1.4 because in this case it works better than without oil.
For darkfield oil is more important: AFAIK you can't get darkfield with objectives with NA>0.75 without an oil DF condenser like the Zeiss Ultracondenser
A condenser labelled 0.9 or smaller must be used dry.
A condenser labelled >0.9 must be oiled to to the slide to reach its nominal NA, if used dry it could get 0.9 maximum. This only will matter for immersion objectives.
The need of a condenser with NA>0.9 is not so clear. In fact many top quality microscopes today use dry 0.9 condensers. In theory in brightfield for maximum resolution the condenser NA must match the objective NA, but to get enough contrast you need to close the aperture, lowering the NA about 20-30%....
I use an achromatic aplanatic 1.4 condenser and compared to a simpler 0.9 the difference is barely noticeable in most cases, and I suspect it is due to its superior optical correction. I use it oiled mainly for DIC with objectives with NA 1 to 1.4 because in this case it works better than without oil.
For darkfield oil is more important: AFAIK you can't get darkfield with objectives with NA>0.75 without an oil DF condenser like the Zeiss Ultracondenser
Pau