A Rheinberg Illumination Challenge

[The QCC]

Not exactly a gauntlet thrown in your face challenge, but more a wet noodle at your feet.
The challenge is to see whether the effects I observe through my microscope can be duplicated or refuted by you, a MicrobeHunter Forum member.
This page on the Olympus Microscopy Resource Centre sets out the rules of engagement.

The linked slideshow demonstrates my use of three Rheinberg stops with three objectives.
I used three Rheinberg filters. Filter #1 has a clear annular ring. Filter #2 has a solid colour ring. Filter #3 has a dual colour ring.

My premise is Rheinberg illumination has a low effect with low power objectives (4x) and works best with 10x obj. and above. Rheinberg illumination also shows better effects with simple (one to three items) specimens.
Hey! I like a challenge so I used a mineral thin section. Also there is still snow on the ground and ponds are still skateable.
Also observed, stopping down the Condenser Aperture reduces or eliminates the effect of the annular ring of the Rheinberg stop. Using only the centre portion. A reversal?
To give you even odds, I did not adjust the height of the condenser.

Have you selected your micro weapon of choice and your Seconds?

ThreeFilters.jpg (39.9 KiB) Viewed 5147 times

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Details:
Microscope: Bausch & Lomb, monocular (c1944)
Objectives: Plan 4x, 10x, 40x
Rheinberg stops: three randomly selected from set of 12
Lighting: LED, 10W variable intensity
Camera: Canon XS (1000D)
Photo eyepiece: Nikon PE 2.5x
Image capture: Canon EOS Utility
Post processing: Colour Science Editor & Adobe Lightroom
Web page: RedRex Base Gallery

[JimT]

Meet me at dawn under the dueling oaks
I have made a bunch of these filters and use them often. Sometimes they provide interesting effects. Especially with an oblique lighting filter.
I lay mine on the LED lamp and find they work best with the 4x, 10x, and 20x objs.
We'll see if anyone takes up the challenge.

[The QCC]

Would it help to get challengers if I offered a free, all expenses paid, one way trip to the fourth circle of Hell?

The 4th Circle: Those who spend a lot of money on stuff they don't need

P.S. I will try laying them on the light source, even though that is very definitely the wrong place to put them.

[gekko]

I might take the challenge to the extent that I understand what one is supposed to do: take some pictures using Rheinberg filters and different objectives? Or are there other conditions? Is there a deadline for submissions?
Some comments according to my present understanding, for what they're worth:

My premise is Rheinberg illumination has a low effect with low power objectives (4x) and works best with 10x obj. and above. Rheinberg illumination also shows better effects with simple (one to three items) specimens.

Your premise is probably correct when the Rheinberg filter is designed for the 10x objective and used with a 4x objective. As far as the 2nd part, I don't see why, in principle, restricting the number of specimens will necessarily give better results technically, although esthetically is a different matter.

Also observed, stopping down the Condenser Aperture reduces or eliminates the effect of the annular ring of the Rheinberg stop. Using only the centre portion. A reversal?

If you reduce the aperture, you will reduce or prevent light from passing through the outer (annular) ring so I think your observation is right on, and in that case the Rheinberg filter will be acting (more or less, depending on how far the aperture is closed) simply as a color filter. I'm not sure what you mean by reversal.

P.S. I will try laying them on the light source, even though that is very definitely the wrong place to put them.

I fully agree: not a good place for Rheinberg filters (or DF stops, for that matter).

[JimT]

I knew Gekko would say that filters don't belong on the lamp

My LED lamp is about 10mm below the filter holder so not too bad. The advantage is I cut them the size of a US silver dollar (~38mm). Getting perfect circles and the exact center is less critical and I can move them around to try for the best illumination.

[The QCC]

In practice, the Rheinberg stop is below the condenser and the condenser aperture is wide open.
So, if JimT's Rheinberg stop is parallel to the bottom condenser lens and at 90° to the light path and the centre stop is "large enough in diameter so as to prevent light from directly entering the microscope objective" the placement of the stop should not be a concern.

But, the centre spot size and shape are critical. The further you get away from the bottom condenser lens, the centre spot must be larger.

JimT. Please post some comparison photos of differet centre spot sizes to qualify for your Rheinberg Challenge prize.

[JimT]

No pictures available and I will not be claiming the prize. Don't need a trip to the fourth circle of Hell. I already am a "Frequent Flyer"
Center spot is about the size of a US penny ~ 18mm for the 4x and 10x obj's. and about the size of a US nickel for the 20x obj. ~22mm (which doesn't work as well as the first two).

JimT