Df, polarized.

[Phill Brown]

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I know there is so much that would improve the image, maybe I have lowered the bar too far.
1mp phone camera squeezed down to fit through the forum letterbox.
Dark field patch, linear polarised, Chinascope.
Not stacked. 20x .4.
Cost of filters £8.
Includes using the plastic case the filter came in below the condenser rather than coloured filters.
Victorian slide from Barbados via eBay.
Cheap as chips, life's good.

[Phill Brown]

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Strew diatoms.
Not DIC as such.
Polarised to extinction,dark field patch.
All dark until adding a plastic Petri dish below the condenser.
I plan to continue lowering the bar until someone says please stop there,
Hoping to learn focus stacking before I'm too past it,1mb phone camera.

[ldflan]

Interesting. Petri dish functioning as wave retarder? I guess. Did you set it up for true darkfield before adding the polarizers? Am thinking probably not, that this must be oblique lighting and not true DF. What happens when you turn the polarizers slightly away from the extinction point?

[Phill Brown]

Most likely poor control.
Set up DF,set up extinction,change to 40x .4, back to DF....make that oblique?
I'll get my coat,it was raining and I was supposed to be doing something outside.
The images are not like phase with coloured filters,tried to avoid moving the polariser,only blue tacked down while moving the petri dish and turning the lid to give many colour combinations.
Good value experiment anyway.

[Phill Brown]

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At the risk of replying to my own thread.
Moss with some dried residue. 10x .25.
The DF patch is slightly misaligned, still giving DF,the second image is just adding plastic below the condenser.
It's only to show what happens.

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Last is full DF, polarised with plastic.
All with full extinction. Checked that.
Should add, used a filter case as the colours are easier to keep control of.
Last is unstacked 200x,DF patch slightly off.
The phone camera doesn't pick up the effect of depth from the binocular head and is missing most of the resolution, remove the plastic and it goes dark mostly.
I built much of the first prototype of 3D TV using LCD glasses and reckon this is better value.

[ldflan]

Acrylic is depolarizing the light, then.

[Phill Brown]

Acrylic is depolarizing the light, then.

I would hope it's an easily repeatable experiment on a budget, I used a Chinascope which has a fixed stage and LED,it is ∞ optics if that makes a difference.
I have a Labophot 2 trinocular with phase 2 1.25 and dedicated filter holders but that ramps up the budget and is chalk and cheese.
In the experiment the DF stop is still blocking direct light untill the acrylic is put in the light path.

[richbart]

I think this is a very interesting technique. I’m go8ng to try it. I have some linear polarized film and a few diffent retarders. I really like the pictures of the diatoms.

[Phill Brown]

As with rainbows they don't come out well with a 1mp digital phone camera.
Reproduced resolution is so disappointing but hopefully gives an overall impression that doesn't need a giant leap of imagination.
In the process of sorting a camera and stacking.
The effect I'm after is a rainbow against a blue background with diatoms and radiolaria.
Polarised at blue in the hope that it will resolve better than broad spectrum.

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Added a pic of pinhole aperture in acrylic below the slide/above the condenser lens.
The colours are maybe affected by the focal length and N/A as the objective lens where it interacts with the light path at different wavelengths.
The iris is the Kohler not the condenser with 4x to show, not the images taken which are within the aperture at 20x & 40x.
Always happy to be corrected.
Material is the base of a plastic food tray. Stress lines cause the DF lighting.
The aperture size should be easy enough to control with how far the pin is pushed through.

[Phill Brown]

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Apologies for resorting to replying to my own thread to reattach and delete.
I'm not quite up to this task.