Olympus condensers

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ZodiacPhoto
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Joined: Sat Sep 24, 2022 6:53 pm

Olympus condensers

#1 Post by ZodiacPhoto » Sat Mar 04, 2023 4:39 pm

My Olympus BX40 scope is equipped with a standard 1.25 Abbe condenser. When focusing the condenser on the field diaphragm opening to set Kohler illumination, the contrast between the opening and the dark areas around it is rather low, and there is excessive color fringing around it. Interestingly, if I insert a 1.25 Abbe condenser from my Meiji Techno scope instead (it fits), the contrast is much better!
My question is, would a different Olympus condenser, either an Aplanat Achromat 1.4, or a Swing-out 0.9 Achromat produce better contrast and less aberrations, and if yes, which one (1.4 or 0.9) should I get? As a side note, I don't use either 2x or 100x objectives, so that criteria is not important for me.
Thank you!

apochronaut
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Re: Olympus condensers

#2 Post by apochronaut » Sat Mar 04, 2023 5:15 pm

One possible difference between the Olympus condenser and the Meiji would be the actual diameter of the lenses. Abbe condensers of 1.25 N.A. only provide their stated N.A. when oil immersed and over a narrow field. Once you go off axis outside of the central sweet spot the N.A. falls off dramatically. AO and PZO used this to advantage, making in the former case an abbe aspheric and the latter an abbe that had unusually wide lenses, so the well corrected part of the field was covered a wider f.o.v. I don't know the Meiji condenser but maybe that is the case? Or it could be a 3 lens abbe, which are usually better.
Colour fringing in proximity to the leaves is normal for poorly corrected condensers as well as a degree of flare. You can use that colour fringing to critically align the condenser, illuminator, field diaphragm axis. When properly aligned the colour fringing should be perfectly even all around the aperture.

For sure , a well corrected condenser is worthwhile. Condensers that are designed to be oiled, so any with an N.A. over 1 do not function the best unoiled usually. Since you are not using a 100x objective and presumably don't use any other immersion objective, a 1.4 N.A. condenser is overkill and expensive. Your condenser of choice would be a .90 achromat aplanat. No muss, no fuss and cheaper. Usually Olympus stuff is overpriced though.
If you can make it work the AO 1.25 abbe aspheric (cat. # 1970 marked on it) is an under the radar gem and underpriced. It will cover a 4X field with a 20mm f.n. without an aux. lens and in tests I did comparing it to a .90 achromat aplanat with 40X fluorite and planapo objectives ( N.A. .70 and 1.0) I couldn't really see any difference when the 1.25 abbe aspheric was used dry. The secret is the aspheric front lens surface.

PeteM
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Re: Olympus condensers

#3 Post by PeteM » Sat Mar 04, 2023 5:24 pm

A better-corrected condenser should help the color fringing you're seeing. As Phil suggests, the Olympus .90 swing-away condenser would be a good choice.

The lack of contrast may be partly an issue of the objectives if they scatter light excessively. Are they Olympus Plan or UPlanFl and in good shape?

ZodiacPhoto
Posts: 59
Joined: Sat Sep 24, 2022 6:53 pm

Re: Olympus condensers

#4 Post by ZodiacPhoto » Sat Mar 04, 2023 5:26 pm

Thank you apochronaut,

I will look at non-Olympus condensers - saving some dough is important to me, and microscopy is just a hobby.
I don't think AO condenser will fit, but I can 3d-print a dovetail adapter if needed.

ZodiacPhoto
Posts: 59
Joined: Sat Sep 24, 2022 6:53 pm

Re: Olympus condensers

#5 Post by ZodiacPhoto » Sat Mar 04, 2023 5:29 pm

PeteM wrote:
Sat Mar 04, 2023 5:24 pm
A better-corrected condenser should help the color fringing you're seeing. As Phil suggests, the Olympus .90 swing-away condenser would be a good choice.

The lack of contrast may be partly an issue of the objectives if they scatter light excessively. Are they Olympus Plan or UPlanFl and in good shape?
Yes, the objectives (Olympus Plan N 4x, 10x, 20x and 40x) are like new optically.

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Olympus condensers

#6 Post by apochronaut » Sat Mar 04, 2023 11:22 pm

ZodiacPhoto wrote:
Sat Mar 04, 2023 5:26 pm
Thank you apochronaut,

I will look at non-Olympus condensers - saving some dough is important to me, and microscopy is just a hobby.
I don't think AO condenser will fit, but I can 3d-print a dovetail adapter if needed.
The dovetail mounting flange, dovetail and filter tray on the AO 1970 are an integrated machined aluminum structure mounted on the bottom of the condenser with 3 cheese head screws. It can be removed in less than 2 minutes. It would need to be replaced with an equivalent roughly 60mm flange and attached appropriate dovetail .The AO dovetail is something like 45mm min. and 48mm max. I don't know how that compares to Olympus. The incoming aperture to the aspheric front lens is about 32mm.
The condenser was actually a Reichert, Buffalo condenser due to the corporate tiptoeing that was going on, so searching under Reichert to find that one might be necessary but usually AO is also effective.
If you want one, I have an extra.
Here is one at a better price because I have to ship from Canada. https://www.ebay.com/itm/144568992729?h ... R7yQou_VYQ

PeteM
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Re: Olympus condensers

#7 Post by PeteM » Sun Mar 05, 2023 3:36 am

The Olympus BH and BX dovetails are around 47mm at the bottom, with a 60 degree angle to the top. Someone with a lathe, even a wood lathe, might be able to turn down the AO/Reichert condenser dovetail ring to fit?

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