Can you see the difference? Köhler illumination

[The QCC]

The links below are to two large photos of Nepheline Syenite as observed through a 10x objective and crossed polars.

Photo 1 has the field iris set to wide open and the condenser aperture stopped down to obtain maximum contrast and resolution. A basic scenario for microscopes without a field iris.

Basic illumination

NephelineSyenite_5OLX10x_13_noKo.jpg (98.41 KiB) Viewed 12238 times

[/url]
In Photo 2 the microscope was setup for Köhler illumination for the 10x obj.. The condenser aperture was stopped down to obtain maximum contrast and resolution.

Köhler illumination

NephelineSyenite_5OLX10x_14_Ko.jpg (103.62 KiB) Viewed 12238 times

[/url]
The method used for setting up Köhler illumination is quite simple and is illustrated in this presntation from Berkley University.

There is sufficient difference to warrant setting up Köhler illumination if your microscope has a field iris.

Microscope: Labomed LB-591, 100w Halogen light source
Camera: Canon 5D MkII
Camera adapter: OMAX 2.5x relay
Specimen: Thin section Nepheline Syenite

[Dale]

I cannot. I spent a few minutes comparing resolution with the images expanded.
Is there a specific part of the specimen I should be looking at?
Dale.

[The QCC]

Did you look at the large images? Right click on the small images to open the large image in separate browser window.

[Dale]

Still no, but the comparison at the Berkley site showed some. I believe the photography leaves some
thing to be desired, as I can see a real difference with my own equipment. Nice concise 7 step procedure
tho.

[The QCC]

If you cannot see the difference between the two large images I have to assume you are not using a monitor calibrated to the sRGB colour space.
My display is factory calibrated to show 95% of the AdobeRGB colour space, but I assign the sRGB profile to the photos for this forum.

There are distinct differences in the shadow areas.

[Crater Eddie]

Sorry, I can barely see any difference in the photos either.
CE

[The QCC]

Oh well, that's life the Internet world of colour.
The difference in quite noticeable in an A-B comparison in FireFox, Internet Explorer and Chrome on all three of my displays.

[mrsonchus]

Same here - the differences are there but no more significant than what may be achieved with a very slight tweak from any image processing program such as Photoshop. The image delivery of everyday computer screens comes nowhere near to being of high enough fidelity to make Kohler relevant as seen on the computer screen - pretty much regardless of colour-spaces etc, which are an absolute minefield of variation and subjectivity in use as opposed to theory - in my limited and of course strictly amateur experience.
Now, in the real-world of the eyepiece-eye-brain combination things are very different indeed (in my experience that is to say, with my 'reasonably priced' Chinese 'scope and all it's limitations), Kohler makes a significant difference to my observations and is very easy and quick to use with such a suitably-equipped 'scope.
It's possible too that perception of a subject that our brain knows for certain to be flat by it's nature - in this case a ground and polished rock/mineral, gives us a different impression to that from a subject that, although we know is similarly flat (it being after all a very thin section also) such as plant or animal tissue (cells are, we know for certain and probably 'see' as such, 3-dimensional, however flat and thin they may be) causing us to appreciate Kohler more. The subtle augmentation given by true Kohler may be subject-dependent and probably almost always of little relevance when seen via an electronic image, colour-spaces and equipment excellence notwithstanding?

That's my personal experience, for what it's worth.

[The QCC]

For what it is worth, the difference I can see is also seen and printed by my HP DJ 130PS printer.

P.S.
In the colour world ICC profiles are not a minefield, but a godsend to consistent colour.
As stated earlier, my monitors are calibrated to the AdobeRGB colour space and my printer and papers are profiled to print what is displayed to the capabilities of the paper.
ICC colour profiling works. It just takes discipline.

[mrsonchus]

For what it is worth, the difference I can see is also seen and printed by my HP DJ 130PS printer.

P.S.
In the colour world ICC profiles are not a minefield, but a godsend to consistent colour.
As stated earlier, my monitors are calibrated to the AdobeRGB colour space and my printer and papers are profiled to print what is displayed to the capabilities of the paper.
ICC colour profiling works. It just takes discipline.

They (ICC profiles) are in my experience indeed a minefield - in practical use not theory, in which they are of course the solution to a difficult, ubiquitous and important problem. I personally do not consider myself lacking in discipline only expertise and a level of spending-power that would allow me to purchase equipment such as you mention - yes I'm sure that some is available at a reasonable price, but to me, the differences, as I have also said earlier, are, in the context of computer screens and imaging paraphernalia available to enthusiasts with resources, expertise and goals comparable to mine, both impractical and barely relevant. The sharing of pictures on the internet is not exactly a high fidelity environment in which to view photo-micrographs or indeed many other types of image... The Pictures you have kindly posted show, to me pretty clearly and it would seem to others, a difference very easily achieved with minimal and basic processing.

I also reiterate my musings, again personal to myself, regarding the subject of the pictures and the inherent 2-D nature of ground & polished rock/mineral slides. They are beautiful and a great achievement for certain, but I think quite different to tissue when viewed and imaged through a microscope.

Nothing it would seem, can better the 'live-viewing' of a slide through a microscope!

I suppose I would need the same equipment and discipline that you demonstrably have, to fully appreciate your beautiful images with Kohler, but for now at least I'll have to settle for the usual internet-images via which they are necessarily shared with others.

Just my own thoughts of course, I can't speak for anyone but myself.

[75RR]

Köhler is not about colour (though it undoubtedly improves), it is about greater resolving power.
The subject matter in the test is not ideal, diatoms from a Kemp 8 Form Test for example would provide a much better evaluation.

Link shows Diatoms from the Kemp 8 Form Test being used to test resolution.
http://www.microscopy-uk.org.uk/mag/ind ... -test.html

[mrsonchus]

That's a very handy link 75RR - thanks for the tip.

[Dale]

Thanks for the link, it was very helpful. My laptop does not have any exotic adjustments, so I stay out of the
minefields.
Dale

[gekko]

Thank you, 75RR, for the very interesting link.

[billbillt]

Great link, but I can't tell any difference between the two...

[Rodney]

I looked at the 2 photo`s for at least 5 minutes. Take a look at the very bottom left of each photo of what looks like a little volcano and compare the 2. It seems to me the second photo has a little more contrast in this area, and when I say little, not much. I would agree the pictures are very close. But I don`t have the best eyes in the world either.

Rodney

[vasselle]

Bonjour
A tous.
Sur mon écran qui est calibré avec une sonde Spyder je vois très bien la différence entre les deux photos.
A ceux qui non pas écran calibré je leurs recommande car on na plus de mauvaise surprise sur la colorimétrie de l'image.
Cordialement seb

[mrsonchus]

Bonjour
A tous.
Sur mon écran qui est calibré avec une sonde Spyder je vois très bien la différence entre les deux photos.
A ceux qui non pas écran calibré je leurs recommande car on na plus de mauvaise surprise sur la colorimétrie de l'image.
Cordialement seb

Aha - a solution within my budget! Thanks for this info vasselle - this looks just the job for my system at a price I can afford (in a while..). The version 5 is out and it's about £95 - not by any means cheap, but not unrealistic either.
I'm going to get one as soon as I can afford to - I've tried - and failed miserably, to match my monitor and printer - this looks like a solution - it would be great too to take advantage of Kohler in captured images as well as live! Many thanks for this very good idea.



This looks like it will enable me to get the full benefit of the QCC's beautiful images also!

[The QCC]

mrsonchus:

To accurately print what you see on the screen within the limits of your printer, calibrate your monitor with a hardware device like the Datacolor Spyder or the Xrite Colormunki.
Set your printer's colour management to sRGB and use a quality photo paper.

The above give satisfying results.

[mrsonchus]

Hi, yes, the spyder seems to fit the bill nicely - I'll buy one pretty soon, after a trip to Scotland I've got coming up.