Author Topic: UV Nikkor 105mm and polarizer  (Read 966 times)

Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #15 on: April 11, 2020, 16:40:28 »
Polarization is an effective tool in photography and cross-polarization is well know to allow to suppress shine and reflections from certain surfaces.

Here a few tests I have made after having been able to find suitable UV polarizers using a glass vase standing on an aluminum lab jack.

Visible light on top, reflected UV light at bottom. Zero, 45 and 90 degree polarizer angles (left to right).

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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #16 on: April 11, 2020, 16:42:34 »
Very nice Klaus.

Did you test the old Zeiss Bernotars as well?

Yes I did, they somewhat work, but not very deep into UV and with rather low transmission...
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Alaun

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Re: UV Nikkor 105mm and polarizer
« Reply #17 on: April 11, 2020, 18:26:20 »
The Zeiss Bernotar were introduced in the 1930ies. I have found a paper from 1939/1940 by J. Wempe testing it for astronomy purposes. He has a transmission chart in that paper showing a strong drop down past 400nm. At 365 it was already very close to zero.  In that paper it is also mentiones, that Zeiss made some special Bernotar filters „with very clear glass“, that were good a bit deeper into UV.

The picture with the aluminum is interesting, as the reflection on the „metal“ is going down as well. Maybe that is because there is always an oxide layer on Al, though only a couple of nm thick (you can grow it into the micro meter range). This layer is used in metallography on Al to reveal the crystal orientation of grains. The samples are polished, anodized (Barker) and then investigated with polarized light. Different orientation then gives different colors.   
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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #18 on: April 12, 2020, 01:47:35 »
The Zeiss Bernotar were introduced in the 1930ies. I have found a paper from 1939/1940 by J. Wempe testing it for astronomy purposes. He has a transmission chart in that paper showing a strong drop down past 400nm. At 365 it was already very close to zero.  In that paper it is also mentiones, that Zeiss made some special Bernotar filters „with very clear glass“, that were good a bit deeper into UV.

The picture with the aluminum is interesting, as the reflection on the „metal“ is going down as well. Maybe that is because there is always an oxide layer on Al, though only a couple of nm thick (you can grow it into the micro meter range). This layer is used in metallography on Al to reveal the crystal orientation of grains. The samples are polished, anodized (Barker) and then investigated with polarized light. Different orientation then gives different colors.   

Here, I measured the transmission(s) as I found two types of Bernotar (maybe older/younger); indeed it does drop in transmission significantly beyond 400nm. But Zeiss Jena made dedicated UV polarizers, too which work to 300nm and beyond. Interesting about the aluminum.

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Alaun

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Re: UV Nikkor 105mm and polarizer
« Reply #19 on: April 12, 2020, 18:57:06 »
That graphs are taken with non pol. light. The polarisation effect drops in to the red, so the transmission increases there. The graphs in the above mention paper are very similar to yours, but not as detailed.
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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #20 on: April 15, 2020, 09:50:34 »
That graphs are taken with non pol. light. The polarisation effect drops in to the red, so the transmission increases there. The graphs in the above mention paper are very similar to yours, but not as detailed.

Yes Werner, I have the published Zeiss Jena graphs too and they are quite similar to mine,
also what they published about their UV polarizers which I'm happy to have found.
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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #21 on: April 15, 2020, 14:24:44 »
So today about Lewisia - Cliffmaids in reflected and polarized light

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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #22 on: April 19, 2020, 20:47:10 »
Well this is a bit on the scientific side, sheet Mica in polarized UV and visible light, different pol. angles.
If interested about the colors and why, I refer to the work of Mr Michel-Levy https://en.wikipedia.org/wiki/Polarized_light_microscopy#The_Michel-Levy_chart

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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #23 on: April 22, 2020, 00:44:02 »
Different approach used here, delivers more intense colors...

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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #24 on: April 27, 2020, 17:28:35 »
Gazania rigens in polarized reflected UV light

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Dr Klaus Schmitt

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Re: UV Nikkor 105mm and polarizer
« Reply #25 on: April 30, 2020, 02:16:30 »
And there is an interested effect possible, I call it the "MIDAS effect" ...



and SILVER also works...



and no plant was harmed doing this, an no spraycan was used ;-)
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