A small comparison between two Zeiss turret phase contrast condensers

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Hobbyst46
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A small comparison between two Zeiss turret phase contrast condensers

#1 Post by Hobbyst46 » Thu Oct 03, 2019 4:38 pm

Hi all,

I have been using the following condenser for a long time:
Achromatic-aplanatic brightfield-darkfield phase-contrast condenser V Z 1.4 (465277)

Yesterday a friend gifted me the following:
Phase-contrast condenser II Z with swing-out lens swinging out 0.9 (465270)

That apparently had been lying unused for many years. The iris aperture was frozen and the top flat glass cover was broken (I was gifted with a spare glass plate, though). This plate is held in place by means of a ring affixed with three tiny screws.
Repair was easy: replacement of the top glass plate; repeated rinsing of the iris aperture leaves with petrol-ether, then drying; cleaning the axle of rotation of the phase-contrast centration levers. A couple of hours later, the phase contrast condenser is alive and kicking.

It is not achromat, so when I close down the field aperture when setting Kohler, color fringe patterns are obvious. However, I would like to see what happens in actual use. It has phases Ph1, Ph2, Ph3. I do not have a 10X Ph1 objective; and, the condenser being of NA 0.9, I did not try objectives of NA>1 yet. My favorite phase contrast objective is the 40X0.75 Neofluar Ph2 (dry).
So here is a small comparison between the two condensers: achromat aplanat 1.4 condenser (abbreviated as 1.4 in the image titles) and the humble 0.9 condenser. All Ph2 setting with the 40X0.75. Single images, resize only.

BTW, both condensers have empty ports; I have tried in the past to occupy them with home-made Rheinberg filters, but finding the right size and centration proved to be time consuming.

Comments are welcome.
Attachments
revived phase condenser II Z, NA=0.9 with top lens (1).jpg
revived phase condenser II Z, NA=0.9 with top lens (1).jpg (43.24 KiB) Viewed 190 times
revived phase condenser II Z, NA=0.9 with top lens (2).jpg
revived phase condenser II Z, NA=0.9 with top lens (2).jpg (42.17 KiB) Viewed 190 times
Diatom1 0.9.JPG
Diatom1 0.9.JPG (79.34 KiB) Viewed 190 times
Diatom1 1.4.JPG
Diatom1 1.4.JPG (78.5 KiB) Viewed 190 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

Hobbyst46
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Re: A small comparison between two Zeiss turret phase contrast condensers

#2 Post by Hobbyst46 » Thu Oct 03, 2019 4:40 pm

(Continued)
Here are some more samples. The preliminary conclusion is - cannot see an important difference in performance.
Possibly, diatoms are not the best test specimens, because of refractions and reflections within the frustules.
Attachments
Diatom2 0.9.JPG
Diatom2 0.9.JPG (63.42 KiB) Viewed 189 times
Diatom2 1.4.JPG
Diatom2 1.4.JPG (63.22 KiB) Viewed 189 times
Diatom3 0.9.JPG
Diatom3 0.9.JPG (68.8 KiB) Viewed 189 times
Diatom3 1.4.JPG
Diatom3 1.4.JPG (68.11 KiB) Viewed 189 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: A small comparison between two Zeiss turret phase contrast condensers

#3 Post by MicroBob » Thu Oct 03, 2019 5:26 pm

Hi Doron,
this is a very interesting comparison. Your old phase condenser is in theory of the best corrected type, the new one is fairly simple but used a lot on good Zeiss microscopes with high new prices, like the Phomi 1.
I have an DIC-alt condenser which is similar to your old condenser, just different use of the ports. I also have a n.a. 0,9 swing in lens condenser (no turret) which is probably optically the same as your new phase condenser.
What i recognized in an instant when mounting the 0,9 condenser: The image of the field aperture is so colourful and unsharp that it is difficult to set Köhler illumination at high magnifications. This is unconvenient but the question is what does it do to the optical performance once set up properly?
I follow your conclusion that there is no real difference in the images you showed here. On the other hand side I'm quite sure that there are applications where the difference shows - but what are they?
- High magnification work? Maybe with a condenser of similar correction state but higher n.a.?
- Colurful objects?
- Objects in fore- and background?

I have the condenser of our groups Universal here for refurbishment - it is gummed up and the microscopes light path was not centered properly when we used it for blood slides last time. Maybe I can contribute more when I check this condenser.

The Phomi 1, second edition, has two field apertures, you change between them with a swing in lens in the condenser holder. This could be quite a challenge for the condenser too.

Bob

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75RR
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Re: A small comparison between two Zeiss turret phase contrast condensers

#4 Post by 75RR » Thu Oct 03, 2019 5:41 pm

.
Don't see much/any difference myself.

These two quotes from Light and Video Microscopy by Randy Wayne may shed some light:

"Spherical aberration can be reduced by replacing a biconvex lens with two plano-convex lenses, or by using an aspherical lens.
Lenses that have been corrected for spherical aberration are known as aspheric, aplanactic, achromatic, fluorite, and apochromatic, in order of increasing correction."


"Lenses corrected for chromatic aberration are labeled achromatic, fluorite, and apochromatic, in order of increasing correction.
These compound lenses are made by putting together a plano-concave lens made out of flint glass with a biconvex lens made out of crown glass,
such that each lens cancels the chromatic aberration of the other one while still focusing the rays."
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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ImperatorRex
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Re: A small comparison between two Zeiss turret phase contrast condensers

#5 Post by ImperatorRex » Thu Oct 03, 2019 6:22 pm

What i recognized in an instant when mounting the 0,9 condenser: The image of the field aperture is so colourful and unsharp that it is difficult to set Köhler illumination at high magnifications. This is unconvenient but the question is what does it do to the optical performance once set up properly?
I follow your conclusion that there is no real difference in the images you showed here. On the other hand side I'm quite sure that there are applications where the difference shows - but what are they?
The only difference is that you need to open the field aperture a bit more, so that the colors get out of sight. Does not make a real difference. The 1.4 n.A. Condensor just makes a difference if you immergate for higher n.A. Some info from the Carl Zeiss technical handbook:

Image

MicroBob
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Re: A small comparison between two Zeiss turret phase contrast condensers

#6 Post by MicroBob » Thu Oct 03, 2019 7:07 pm

Hi Jochen,
thank you for this source!
Zeiss states that the better corrected condenser is useful for higher magnifications and colour photography and they give the advise to open the field aperture a bit more to avoid a negative influence of the coloured aperture edge.

Bob

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75RR
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Re: A small comparison between two Zeiss turret phase contrast condensers

#7 Post by 75RR » Thu Oct 03, 2019 7:37 pm

Zeiss states that the better corrected condenser is useful for higher magnifications and colour photography and they give the advise to open the field aperture a bit more to avoid a negative influence of the coloured aperture edge.
Thanks! Could not face typing all that out in a translation software :)
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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