Condensers...

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Sauerkraut
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Condensers...

#1 Post by Sauerkraut » Fri Jun 21, 2019 7:51 pm

Just curious. Is it straightforward to swap/upgrade condensers amongst different manufacturers if they have the same numerical aperture, design, and fit in the holder/allotted space?

Mine has an internal green speck on the lens that shows clearly at the lower powers when Kohler illumination is achieved. I can blur the speck by lowering the condenser a bit. Admittedly this small adjustment doesn't seem to affect image quality but the obsessive part of me is annoyed by the speck. Disassembly of the condenser feels precarious (offending speck is inside the lenses, not outside), if only because it doesn't look obvious how to do it and also, I can't find an OEM replacement so if it was to somehow get damaged, the scope would be out of commission.

Heather

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Re: Condensers...

#2 Post by Hobbyst46 » Fri Jun 21, 2019 9:31 pm

Is the green speck in focus when you focus on the specimen ? I am asking, because under proper Kohler illum., the condenser is NOT in focus.
Perhaps the speck is elsewhere ?
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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mrsonchus
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Re: Condensers...

#3 Post by mrsonchus » Fri Jun 21, 2019 9:48 pm

I had a very similar problem - turned out to be a speck on the mirror.....
John B

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Re: Condensers...

#4 Post by Sauerkraut » Fri Jun 21, 2019 11:01 pm

Hobbyst46 wrote:Is the green speck in focus when you focus on the specimen ? I am asking, because under proper Kohler illum., the condenser is NOT in focus.
Perhaps the speck is elsewhere ?
I follow the Kohler illumination procedure step where the field iris diaphragm is focused by moving the condenser until the edges of the diaphragm are crisp. Once this is done, I can see the green speck. By lowering the condenser just a touch, the speck blurs and is less noticeable. At higher magnifications I don't see the speck. Just a minor irritation but still...

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Re: Condensers...

#5 Post by Sauerkraut » Fri Jun 21, 2019 11:07 pm

mrsonchus wrote:I had a very similar problem - turned out to be a speck on the mirror.....
I've put the condenser under the stereo scope and can see the speck is seemingly in between the lenses of the condenser. I'm not very familiar with condenser construction but there appears to be 2 lenses(?).

I just figured it might be of interest to upgrade my condenser (say to one with a thicker capacity filter holder) while also dealing with that speck.

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Re: Condensers...

#6 Post by mrsonchus » Fri Jun 21, 2019 11:21 pm

If you post an image of your condenser someone here's certain to know how to take the lenses apart. With my Leitz condenser the top lens (2-lens assembly) simply unscrewed into it's two component lenses - they were very stiff to unscrew but I used a grip around a soft cloth to do it.
John B

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Re: Condensers...

#7 Post by Hobbyst46 » Sat Jun 22, 2019 9:43 am

Sauerkraut wrote:
mrsonchus wrote:I had a very similar problem - turned out to be a speck on the mirror.....
I've put the condenser under the stereo scope and can see the speck is seemingly in between the lenses of the condenser. I'm not very familiar with condenser construction but there appears to be 2 lenses(?).

I just figured it might be of interest to upgrade my condenser (say to one with a thicker capacity filter holder) while also dealing with that speck.
Two separate lenses are there for different NAs of objectives. The top one is either screwed in place or is flip-out. It can be removed or flipped out of the optical path for low-NA objectives (typically low power, say <10X). if it is the screw-in type, tt can be unscrewed for inspection of the inner glass surfaces. Usually, finger power is adequate.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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Re: Condensers...

#8 Post by Sauerkraut » Sat Jun 22, 2019 2:55 pm

This condenser is probably not as nice as the ones being used by people on here by the more prestigious microscope manufacturers. It looks like the lens holding part is one piece with 3 small set screws right near the base where it attaches to the iris part.

It's not really a matter of wanting to take this one apart, but rather me wondering if condensers are generally able to be mixed and matched to different scopes. I think by lack of answers along these lines, I've surmised that condensers are not mixed and matched very much. That answers my question in a roundabout way. And maybe if I find something of similar dimensions/N.A. on eBay for a reasonable price, I'll try it anyway and see what happens.

Thanks everyone for the input.

Heather

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Re: Condensers...

#9 Post by Hobbyst46 » Sat Jun 22, 2019 3:19 pm

Sauerkraut wrote:This condenser is probably not as nice as the ones being used by people on here by the more prestigious microscope manufacturers. It looks like the lens holding part is one piece with 3 small set screws right near the base where it attaches to the iris part.

It's not really a matter of wanting to take this one apart, but rather me wondering if condensers are generally able to be mixed and matched to different scopes. I think by lack of answers along these lines, I've surmised that condensers are not mixed and matched very much. That answers my question in a roundabout way. And maybe if I find something of similar dimensions/N.A. on eBay for a reasonable price, I'll try it anyway and see what happens.

Thanks everyone for the input.

Heather
Hi, Heather.
About your question from June 21th, sometimes fixing a small problem might be much easier than finding a suitable replacement.
It is possible to mix and match condensers, especially simple condensers (like Abbe). It is more difficult for condensers that include, for example, phase contrast annuli, since then you might need new objectives.... The three conditions you mentioned must indeed be met, although mechanical modifications are sometimes possible...
So posting a photo and description of your condenser and microscope might help others help.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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Re: Condensers...

#10 Post by Roldorf » Sat Jun 22, 2019 4:30 pm

Perhaps if you take the measurements of your condenser other members can look to see if their condenser's are the same or different. You can look at the manufacturers of those that are the same.
Alan
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Re: Condensers...

#11 Post by Sauerkraut » Sat Jun 22, 2019 5:58 pm

Thanks again for all responses. I’ll leave well enough alone for now with my condenser.

I know a guy who bought a used motorcycle. It had a little cosmetic blemish on an engine part. He ended up taking a bunch of stuff apart to try to address the scratches and to this day, it doesn’t run. Think I’ll learn from that adventure.

Many thanks for all your collective expertise.

Heather

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Re: Condensers...

#12 Post by apochronaut » Mon Jun 24, 2019 12:29 pm

Often, a coloured speck in the condenser is caused by a small scratch or some adhered substance on the upper surface of the top condenser lens refracting.
Give the top lens a really good cleaning with isopropyl but if a scratch, aside from getting another condenser, lowering the condenser slightly is certainly within bounds for appropriate technique.
Another option is to wipe a light smear of immersion oil on the top lens when you use the condenser, which fills in the scratch or oil the condenser to the slide( probably best for 40X and up anyway).

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Re: Condensers...

#13 Post by wabutter » Tue Jun 25, 2019 8:25 pm

Keep in mind that when Kohler illumination is set up, there are only a specific points in the illumination access that are conjugate to the image plane. Correspondingly specific point in the illumination plane. If the image of the speck is in focus, the speck will be at easily defined points. Retina image plane, (that can be ruled out unless you have a severe vision problem): Field stop of the eyepeice, (unless you have a reticle in place this is usually a spot where nothing can adhere), Specimen Plane, ( if you change specimens is it still there) The field diaphragm.( Some microscopes will have heat absorbing glass or filter almost at the same plane as the FD. Those are the places you should be looking. Usually on a accessible surface as well.

Regards,

Wayne

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Re: Condensers...

#14 Post by iconoclastica » Tue Jun 25, 2019 9:58 pm

AFAIK, there are no theoretical objections to using condensers foreign to the brand of your microscope, unless they come along with custom above stage equipment (the phase rings/objectives were mentioned above). But there's also the issue of physical fit. However, if you know your way with e.g. 3d-printers, there are possibilities. This year I retro-fitted two condensers to my Nikon: a cheap abbe (just to see it could be done and use the filter slide) and a nice old Lomo darkfield condenser. It's just a matter of fitting a tube of the proper dimensions on top of the dove tail ring propietary to your microscope type. If you make it modular, the bottom part can be resused with multiple condensers.

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Re: Condensers...

#15 Post by apochronaut » Wed Jun 26, 2019 2:50 am

wabutter wrote:Keep in mind that when Kohler illumination is set up, there are only a specific points in the illumination access that are conjugate to the image plane. Correspondingly specific point in the illumination plane. If the image of the speck is in focus, the speck will be at easily defined points. Retina image plane, (that can be ruled out unless you have a severe vision problem): Field stop of the eyepeice, (unless you have a reticle in place this is usually a spot where nothing can adhere), Specimen Plane, ( if you change specimens is it still there) The field diaphragm.( Some microscopes will have heat absorbing glass or filter almost at the same plane as the FD. Those are the places you should be looking. Usually on a accessible surface as well.

Regards,

Wayne
even if the upper plane surface of the condenser is defocused, a refractive element such as a scratch or adherent substance , can still produce enough of a portion of the spetrum to be visible. I have a .90 dry condenser about 6 ft. from me right now that has that problem. I have to lower it just slightly out of it's correct koehler positioning in order for the purplish mark to go away. However, moving the condenser slightly up and down alters the spectral character somewhat.

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