Condenser Height Adjustment

Do you have any microscopy questions, which you are afraid to ask? This is your place.
Post Reply
Message
Author
tomecki
Posts: 5
Joined: Tue Oct 23, 2018 7:20 pm

Condenser Height Adjustment

#1 Post by tomecki » Tue Oct 23, 2018 7:32 pm

I recently acquired a Wild Heerbrugg M11 microscope. It's equipped with a Swing-out condenser with iris diaphragm (nA 0.65 - 1.30). There is no provision for centering the condenser, so I don't believe it's a Koehler illumination system. I've found lots of info on how to adjust the diaphragm to maximize resolution and contrast. I also know that the top lens should be swung out for low power objectives. I can't find any information on where to set the height of the condenser for optimal performance. Any help would be appreciated.

apochronaut
Posts: 2859
Joined: Fri May 15, 2015 12:15 am

Re: Condenser Height Adjustment

#2 Post by apochronaut » Tue Oct 23, 2018 8:42 pm

The possibility of Köhler with that scope is dependent on which illuminator it is supplied with. The microscope stand itself has no köhler capacity.

Some microscopes have a precentered condenser, which can be adjusted slightly by virtue of playing with the mounting fixtures and some microscopes have centering controls attached to the condenser mount. Either system can be used for köhler illumination, as long as köhler is enabled in the optics of the illumination system.

The height of the condenser is dependent on how you are using it. If you are using it as a .65 condenser , that would normally be because you are using low power and low N.A. objectives. The height can be adjusted to best fill the field with light and would be suitable for up to a .65 N.A. objective.
When using it with the 1.3 N.A. lens swung in, it must be oiled to the underside of the slide in order to be functioning at 1.3. This gives only a tiny amount of lee way for adjustment and normally is only necessary for the oil immersion objective but you can likely use it for the 40X as well.
When using it with the 1.3 N.A. top lens swung in but unoiled, it's N.A. will be somewhere around .90. That is usually the most practical and trouble free method for average use of the two top objectives, as well as with some of lower power. The oil immersion objective will have an N.A. of about 1.12. in such a situation and be suitable for a lot of average work. OIling of the condenser is always an option.
You can only adjust for köhler on that microscope, if you have the köhler enabled illuminator , Q, or other higher grade of illuminator.

User avatar
coominya
Posts: 279
Joined: Sun Mar 11, 2018 11:33 am
Location: Brisbane Aust

Re: Condenser Height Adjustment

#3 Post by coominya » Tue Oct 23, 2018 9:28 pm

As a general rule, I wind mine up to the very top, where it's brightest, and then lower it until I get good contrast. There are specifically stated position settings, but the people writing these in articles I have read usually say, "open it a little past the standard setting" and "adjust the condenser height to improve contrast" This confused me at first, until I realized that while the whole point of these adjustments is to give the theoretical optimum image, my eye ultimately is the best adjustment tool to use. It's also interesting to note how different settings can highlight different detail, so just experiment I would say.

Bryan
Posts: 74
Joined: Mon Sep 17, 2018 11:31 pm

Re: Condenser Height Adjustment

#4 Post by Bryan » Tue Oct 23, 2018 10:05 pm

coominya wrote:As a general rule, I wind mine up to the very top, where it's brightest, and then lower it until I get good contrast. There are specifically stated position settings, but the people writing these in articles I have read usually say, "open it a little past the standard setting" and "adjust the condenser height to improve contrast" This confused me at first, until I realized that while the whole point of these adjustments is to give the theoretical optimum image, my eye ultimately is the best adjustment tool to use. It's also interesting to note how different settings can highlight different detail, so just experiment I would say.
I've been reading articles on this as well trying to figure out how to get the most out of my abbe condenser and that's pretty much the conclusion I have come to.

apochronaut
Posts: 2859
Joined: Fri May 15, 2015 12:15 am

Re: Condenser Height Adjustment

#5 Post by apochronaut » Tue Oct 23, 2018 11:31 pm

If one reads the manuals, theoretically the best position is the highest possible that one can still fill the field, and then the iris is adjusted to be just beyond the aperture of the objective. With most systems, especially older systems, this will result in varying amounts of flare and loss of contrast. If the iris and height are adjusted for maximum contrast, there is usually enough loss of N.A., to lower the resolution. Usually, and increasingly with older systems, the optimum contrast lies somewhere in the middle. If one removes an eyepiece and peeks down the tube, the iris borders will be clearly visible inside the aperture of the objective, when optimum contrast and resolution are achieved. This is considered to be undesirable but it is necessary, in order to work around flare. Objectives have gotten better over the years.

User avatar
ebenbildmicroscopy
Posts: 96
Joined: Sun Jul 23, 2017 8:57 pm

Re: Condenser Height Adjustment

#6 Post by ebenbildmicroscopy » Wed Oct 24, 2018 12:12 am

I have to second what apochronaut said, especially about removing the eyepiece and observing the fringe of the condenser iris. Oddly enough, when I took a microscopy/photomicrography course in college, our lab was equipped with Wild M11 scopes that were also outfitted with the field diaphragm rigged illuminators. As a resolution target, we were all given permanent slides of the diatom Pleurosigma angulatum since, if I remember correctly, the pore pattern of the silica exoskeleton in this species approached the resolving power of a typical transmitted light microscope.

When setting up Kohler with these slides, it was easy to lower the condenser too much or stop down the condenser iris too far to produce an image that appeared almost like the up close pixels on a video screen... a surface resembling black dots. Whereas if the condenser were set to maximize resolution instead of contrast, the same diatom appears to resemble a window screen instead of the dots, so that what had appeared as dots were now clear and defined by the margins of the pores. I still have my Pluerosigma slide from then and use it to test my setups when switching optics around.

In my microscope repair work, I have found that the worst people for misuse of microscope condensers are hospital lab technicians who have to analyze urine samples. They're looking for casts and blood cells, etc. The casts are usually very near clear and in order to increase contrast, the techs will ALWAYS either rack the condensers waaaaayyyyyy down in the basement or stop down the condenser iris. The problem is, you begin ghosting artifacts from other surfaces in the system: maybe dust particles on the bottom lens of the condenser or maybe a smear on the bottom of the specimen slide. It's a big problem because they'll start applying the same technique when they move to the microbiology bench or the blood bench, etc. There are only 2 "In Service" workshops I ever give in hospitals - Use of the condenser is one (for all the reasons just stated), and the other is how NOT to use immersion oil!
JeffO, aka "Ortho amore"
Leitz Ortholux I
Leitz Orthoplan
Leitz Macro-Dia Device
Zeiss GFL
Zeiss Standard
Zeiss Photomicroscope III
Zeiss OPMI 6S
B&L Stereozoom and Balplan

User avatar
KurtM
Posts: 1542
Joined: Tue Jun 09, 2015 12:08 am
Location: League City, Texas
Contact:

Re: Condenser Height Adjustment

#7 Post by KurtM » Wed Oct 24, 2018 1:48 am

I think I get all this stuff pretty well, but how I would love to sit in on one of your workshops! Or spend an afternoon with Apo...

Thank you so much for so generously and consistently sharing your knowledge and experience, gentlemen! I hereby confer upon you both the highly coveted Uber Geek emoticon: :ugeek:
Cheers,
Kurt Maurer
League City, Texas
email: ngc704(at)aol(dot)com
http://sawdustfactory.nfshost.com/microscopes/
https://www.flickr.com/photos/67904872@ ... 912223623/

Grahame
Posts: 99
Joined: Fri Jun 29, 2018 7:42 am
Location: New Zealand

Re: Condenser Height Adjustment

#8 Post by Grahame » Wed Oct 24, 2018 6:41 am

I'm going to concur with Kurt on this.
Informative thread.
As per for me it shows I've been doing things wrong, nothing unusual.
I'm slowly building a frankenstein fotoscope.
When I had less light (10W led) than I do now I was using the condenser as high as possible to get as much light as possible.
Now I'm using a 50W led I have been using it as low as possible to get the highest contrast, I do like the look but now I know I'm losing resolution.
Back to the drawing board.
Thanks folks for yet another education.

tomecki
Posts: 5
Joined: Tue Oct 23, 2018 7:20 pm

Re: Condenser Height Adjustment

#9 Post by tomecki » Wed Oct 24, 2018 5:19 pm

Thanks for taking the time to answer my question, everyone. I've been lurking on here for a few months, but this was my first post and I'm amazed at all the knowledgeable people that take the time to help out a beginner. This forum is great!

User avatar
KurtM
Posts: 1542
Joined: Tue Jun 09, 2015 12:08 am
Location: League City, Texas
Contact:

Re: Condenser Height Adjustment

#10 Post by KurtM » Thu Oct 25, 2018 12:35 am

One of the nice side benefits to having condenser height and field iris properly adjusted is you get a tiny, brilliant spot of light on the slide illuminating the precise point on the slide you're looking. This is useful for marking coverslips with a fine tip Sharpie to locate individual targets.
Cheers,
Kurt Maurer
League City, Texas
email: ngc704(at)aol(dot)com
http://sawdustfactory.nfshost.com/microscopes/
https://www.flickr.com/photos/67904872@ ... 912223623/

Post Reply