Spirogyra

Images made through a microscope. All subject types.

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Marek Mis
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Spirogyra

Post by Marek Mis »

Image

10 X S Plan Apo Olympus, Lumipan - CZJ old microscope
Polarized light (quarter-wave plate and additional retarder)
HF stacked

Pau
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Post by Pau »

Brillant!. Excellent composition and colours.
I'm not a big fan of retarders, but here you got a wonderful effect.
One question: The different colours of the longitudinal and tranversal cell walls, are due to its thickness or to the orientation?. (The defocused algae filaments in th background are near perpendicular and also show the same yellow in the transversal walls) (or are they a phantom image?) :smt017
Pau

Mitch640
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Post by Mitch640 »

Very nice detail and color in this image. Nice find.

Marek Mis
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Post by Marek Mis »

Pau,

I really don't know what is source of difference of colours. Now I think perhaps the main reason is chemical constitution of the cell walls. I don't know. Below I enclose separate image the filaments oriented like those ones below the first layer of filaments in the first image. You can see the transversal walls are the same colour (yellow) but the longitudinal ones are different (green). Perhaps is there anybody who could explain it. :smt102

Image

discomorphella
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Post by discomorphella »

Hi Marek--

Although the formal explanation is somewhat technical, I can give you a simple "hand waving" explanation that will explain most of what you are seeing. If I understand your setup correctly you have a linear polarizer followed by a quarter wave plate in your illuminator, and another linear polarizer after your objective. On closer reading, you may have a full wave plate or half wave plate in there too...not sure from your post. The effect is a well-known function of the birefringence of your sample illuminated by the circularly polarized light (well, elliptically polarized really but don't worry about it) you are providing using your quarter wave plate.
Basically, the layers of cellulose in the cell walls of your algae will form another waveplate. At some wavelengths of light (depending on how thick the layers are and their orientation) the combination of the two waveplates (the one you put in your scope, and the one nature put in your sample) will turn the circular polarized light into linearly polarized light (say in the X direction) and your polarizer will block them. At other wavelengths the combination will result in the orthogonal (Y) polarization and these wavelengths will pass through your upper polarizer. If the combination of sample + waveplate removes blue wavelengths the sample layers will look red, if it removes a wider range around the blue region of the spectrum you will see something more towards orange. Where the combination removes red wavelengths you will observe blue coloration. In your images this shows up clearly where one orientation of the cell walls is orange, and the orthogonal cell walls are green...If you rotate your sample (or the quarter wave plate) 90 degrees you will see the orange layers turn to green and visa versa...since you will have exchanged the orientation of the layers with respect to your polarizers. If the particular strands of algae have slightly differing thickness you will of course see different colors, but the change as you rotate your sample should remain essentially the same.
Hope this is not too confusing, I can post a diagram later if you want.

Regards,

David

Craig Gerard
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Post by Craig Gerard »

Marek,

These images are most intriguing.

If I can achieve similar results just once, then my purchase of a microscope would not have been in vain.

Thankyou for sharing.

Now I'm going to read David's response and try to absorb the detail.

Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Marek Mis
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Joined: Sat Jul 10, 2010 9:56 am
Location: Suwalki, Poland
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Post by Marek Mis »

Hello David,

Thank you very much for your exhaustive explanation ! :lol:

Marek

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