MicrobeHunter.com Microscopy Forum

Hi everyone,
When I read about how to use a condenser, I often came across the advice:
Set the aperture diaphram lever of the condenser lens to "the same value as the NA of the objective lens".


However, my condenser is like this:


How would I use it in the best way then?
Thanks!

Remove an eyepiece and peer down the empty tube … Adjust the diaphragm until it about seven-eighths fills the field of view, or until you are sure that no light is bouncing off the inner wall of the tube.
Make a note of the arbitrary number that Nikon has provided, for your future convenience.

MichaelG.

Having the condenser aperture a bit smaller that the objective NA gives the best xy resolution, but sometimes you want better depth of field which requires a smaller aperture. Abbe discusses this in his 1882 paper https://onlinelibrary.wiley.com/doi/10. ... .tb00190.x

crb5 wrote: ↑

Fri Dec 02, 2022 1:47 am

Having the condenser aperture a bit smaller that the objective NA gives the best xy resolution, but sometimes you want better depth of field which requires a smaller aperture. Abbe discusses this in his 1882 paper https://onlinelibrary.wiley.com/doi/10. ... .tb00190.x

Agreed … but I consider the essential first-step is to set the maximum useable aperture.

MichaelG.

MichaelG. wrote: ↑

Thu Dec 01, 2022 10:32 pm

Remove an eyepiece and peer down the empty tube … Adjust the diaphragm until it about seven-eighths fills the field of view, or until you are sure that no light is bouncing off the inner wall of the tube.
Make a note of the arbitrary number that Nikon has provided, for your future convenience.

MichaelG.

+1
Always good to have an identifiable starting point.

This is a link to the Abbe article on Dropbox: https://www.dropbox.com/s/bwfk3npzp94g4 ... e.pdf?dl=0

Note: No need to join Dropbox to download anything, close any window asking you to sign in - and then just click on the download button top left.

75RR wrote: ↑

Fri Dec 02, 2022 2:47 pm

This is a link to the Abbe article on Dropbox: https://www.dropbox.com/s/bwfk3npzp94g4 ... e.pdf?dl=0

Note: No need to join Dropbox to download anything, close any window asking you to sign in - and then just click on the download button top left.

.
Thanks for sharing that

… am I correct in believing that it is Part_1 of 2 ?

[ see his comment on p.302 ]

MichaelG.

MichaelG. wrote: ↑

Fri Dec 02, 2022 3:43 pm

75RR wrote: ↑

Fri Dec 02, 2022 2:47 pm

This is a link to the Abbe article on Dropbox: https://www.dropbox.com/s/bwfk3npzp94g4 ... e.pdf?dl=0

Note: No need to join Dropbox to download anything, close any window asking you to sign in - and then just click on the download button top left.

.
Thanks for sharing that

… am I correct in believing that it is Part_1 of 2 ?

[ see his comment on p.302 ]

MichaelG.

You are, had missed that.

Here it is: https://www.dropbox.com/s/kjmc1h1kplbcl ... 2.pdf?dl=0

.

You are a Star, 75RR

MichaelG.

Thank you very much, MichaelG and 75RR.
Cheers,

Just a thought on the markings on the Nikon Condenser. In the first picture, the aperture markings appear to be a linear scale (though I realize the diaphragm follows a square-law principle, double the aperture for 4 times the area). So on the Nikon condenser 30 should represent 1.25 and the lowest number on the scale (2?), to the lowest aperture (not sure what that is). So set up a ratio and make a similar linear scale corresponding to the numbers on the Nikon scale, 30=1.25, 25=..., 20=..., etc. Just a thought to get you into the aperture ballpark. (Very good articles, by the way!)