High résolution tests

[Jean-marc]

Hi René,

When I look at diatoms at high magnification with darkfield condenser, I always use polarised light. If not, there are too much light artefact because diatoms diffraction, and the image is not as good.
I have used Zeiss planapo 100/1,30, nikon planapo 100/1,40, and I think the olympus is slighty better.
Just one critic : compared to my Leitz pl Apo 63/1,40 and Fluotar 100/1,32, the olympus is too brightly in the center as you can see.

Are you talking about my frustulia photo ? Do you think there is a problem ?
Best regards

JM

[Pau]

Jean-Marc, some questions about yuour tests:
I'm puzzeled about why you do use a darkfield condenser at this high N.A., because you aren't getting dark field (I think it is not posible), maybe some kind of circular oblique illumination?
And about polarised light, only a polarizer?. I've tried cross polarization with diatoms and it was useless because its silica shell is amorphous and they disapear of the field.

I have used Zeiss planapo 100/1,30, nikon planapo 100/1,40, and I think the olympus is slighty better.
Just one critic : compared to my Leitz pl Apo 63/1,40 and Fluotar 100/1,32, the olympus is too brightly in the center as you can see.
JM

Did you compare all this high end objectives with each own compensating eyepieces (if they are finites) or tube lenses (if infinites) or in the same system? Correction mismatch between optical components may explain this differences.

[René]

Are you talking about my frustulia photo ? Do you think there is a problem ?
Best regards

JM

are we talking cross polarized light or single plane?

And yes, I have the hotspot too with quite a lot of objectives. Might see if a polarizer would be beneficial in that respect..

For our diatomist I did a comparison in the past between Leitz npl fluotar 100/1.32, zeiss neofluar 100/1.3, planapo 100/1.3 en 63/1.4, Olympus splanapo 100/1.4 and 60/1.4 and several achros that I could find. I tried them on a Oly BHS stand with 1.2-1.4 cardioid condenser. No polarizers. The amount of contrast is erratic, not always to do with level of correction. Best result gave the Zeiss planapo 100/1.30.

Best wishes, René

[Jean-marc]

Hi Pau, Rene,

maybe some kind of circular oblique illumination?

Yes Pau, a center stop in high NA condenser is the best way to see critical details in diatoms.

Did you compare all this high end objectives with each own compensating eyepieces

I use periplan GW 10/26, and yes, I tried also with olympus WHK 10/20, it was the same hotspot. I think it is the darkfield light that give this problem, but it was a good idea Pau.

I've tried cross polarization with diatoms and it was useless because its silica shell is amorphous

Yes you are right, but I never crossed totally the 2 polarisers.
I always have best result with polarisers.

Might see if a polarizer would be beneficial in that respect.

No I do not used polariser for avoid this problem, only to have better définition on the diatoms dots.

Best result gave the Zeiss planapo 100/1.30

I have done some tests too, and particulary, I tested 2 Leitz pl apo 63/1,40 against 2 Zeiss planapo 63/1,40.
The 2 zeiss had always a slighty better contrast. But I never have any delamination with a Leitz

Thank you Rene to share your experience with us.

Best regards

JM

[Pau]

Thanks Jean-Marc and René for your explanations.
I will try the darkfield condenser and semi crossed polarizers trics in the future. For now my best results were with a deep blue filter and lateral oblique illumination.
As an amateur, I don't have access to all that planapos to test, but I have a NPL Fluotar 100 1.32 and a Neofluar 100 1.3, both for phase contrast. Is there any real advantage of a 1.4 objective over a 1.3?

[Jean-marc]

Hi Pau,

I see easily dots of A pellucida with my NPL Fluotar 100/1,32. You will lost a bit of contrast because the phase contrast ring inside the objective.

Is there any real advantage of a 1.4 objective over a 1.3?

Yes of course, but it is not the most important when you want to see dots.
NA condenser is more important than NA objective.

A+

JM