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Polarized Reflected Ultraviolet Photography
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PostPosted: Thu Apr 02, 2020 10:10 am    Post subject: Polarized Reflected Ultraviolet Photography Reply with quote
Was doing some testing about using polarizers with reflected UV, so here a few samples presented as gifs while rotating the filter.
This was shot using a modified camera with only fused silica glass in front of the sensor and the Baader-U filter (320-390nm),
lens used was the UV-Nikkor 4.5/105mm and sunlight as light source.

Roofs of some neighbouring houses showing strong polarizing effect of glass windows and metal:



Succulent plant - Lewisia showing strong polarizing effects:



PostPosted: Thu Apr 02, 2020 12:02 pm    Post subject: Re: Polarized Reflected Ultraviolet Photography Reply with quote
kds315* wrote:
Was doing some testing about using polarizers with reflected UV, so here a few samples presented as gifs while rotating the filter.
This was shot using a modified camera with only fused silica glass in front of the sensor and the Baader-U filter (320-390nm),
lens used was the UV-Nikkor 4.5/105mm and sunlight as light source.

Roofs of some neighbouring houses showing strong polarizing effect of glass windows and metal:


Thanks Klaus, how did you manage to find a polarizer that transmits UV?
Those I've looked at have practically no transmission, certainly the Variable NDs (two stacked polarizers) have <0.02% at 400nm.

FWIW metallic reflections aren't polarised - at least in the visible - I think it's highly likely the metal round those roof windows is all painted/lacquered (paint does polarize it's reflections)


PostPosted: Thu Apr 02, 2020 12:10 pm    Post subject: Re: Polarized Reflected Ultraviolet Photography Reply with quote
DConvert wrote:
kds315* wrote:
Was doing some testing about using polarizers with reflected UV, so here a few samples presented as gifs while rotating the filter.
This was shot using a modified camera with only fused silica glass in front of the sensor and the Baader-U filter (320-390nm),
lens used was the UV-Nikkor 4.5/105mm and sunlight as light source.

Roofs of some neighbouring houses showing strong polarizing effect of glass windows and metal:


Thanks Klaus, how did you manage to find a polarizer that transmits UV?
Those I've looked at have practically no transmission, certainly the Variable NDs (two stacked polarizers) have <0.02% at 400nm.

FWIW metallic reflections aren't polarised - at least in the visible - I think it's highly likely the metal round those roof windows is all painted/lacquered (paint does polarize it's reflections)


Thanks for the hint, those may well be painted metal frames indeed!

A fried of mine and I have tested quite a bunch, and I was lucky and found some Zeiss dedicated polarizers for UV, so those work down to 300nm. Later I also found out that some older Heliopan uncoated polarizers (certainly NOT the modern MC coated high transmission ones!) did transmit rather well to about 340nm, and so does some older Zeiss Jena BERNOTAR polarizers, but not as good as the Heliopan ones. The loss is about 2.5-3stops though.



PostPosted: Thu Apr 02, 2020 1:54 pm    Post subject: Re: Polarized Reflected Ultraviolet Photography Reply with quote
kds315* wrote:
DConvert wrote:
kds315* wrote:
Was doing some testing about using polarizers with reflected UV, so here a few samples presented as gifs while rotating the filter.
This was shot using a modified camera with only fused silica glass in front of the sensor and the Baader-U filter (320-390nm),
lens used was the UV-Nikkor 4.5/105mm and sunlight as light source.

Roofs of some neighbouring houses showing strong polarizing effect of glass windows and metal:


Thanks Klaus, how did you manage to find a polarizer that transmits UV?
Those I've looked at have practically no transmission, certainly the Variable NDs (two stacked polarizers) have <0.02% at 400nm.

FWIW metallic reflections aren't polarised - at least in the visible - I think it's highly likely the metal round those roof windows is all painted/lacquered (paint does polarize it's reflections)


Thanks for the hint, those may well be painted metal frames indeed!

A fried of mine and I have tested quite a bunch, and I was lucky and found some Zeiss dedicated polarizers for UV, so those work down to 300nm. Later I also found out that some older Heliopan uncoated polarizers (certainly NOT the modern MC coated high transmission ones!) did transmit rather well to about 340nm, and so does some older Zeiss Jena BERNOTAR polarizers, but not as good as the Heliopan ones. The loss is about 2.5-3stops though.



I can see it would be worth my checking all my old polarizers, I might have some that are usable Smile
It's all too easy to jump straight on e-bay at the moment, but I've got enough extras I've remembered a use for on the way already...
I will note those models in case none of my current ones prove suitable. Thanks for the info!

Last edited by DConvert on Thu Apr 02, 2020 2:25 pm; edited 1 time in total


PostPosted: Thu Apr 02, 2020 2:23 pm    Post subject: Reply with quote
...

Last edited by Blazer0ne on Tue Feb 22, 2022 6:57 pm; edited 1 time in total


PostPosted: Thu Apr 02, 2020 2:31 pm    Post subject: Reply with quote
Blazer0ne wrote:
The animation was a nice touch. Wink

Question, can an X-rite i1 Pro be rigged up to measure spectral response such as the graphs provided?


No, it is only for visible light!


PostPosted: Thu Apr 02, 2020 3:10 pm    Post subject: Reply with quote
...

Last edited by Blazer0ne on Tue Feb 22, 2022 6:57 pm; edited 1 time in total


PostPosted: Thu Apr 02, 2020 4:18 pm    Post subject: Re: Polarized Reflected Ultraviolet Photography Reply with quote
DConvert wrote:
kds315* wrote:
DConvert wrote:
kds315* wrote:
Was doing some testing about using polarizers with reflected UV, so here a few samples presented as gifs while rotating the filter.
This was shot using a modified camera with only fused silica glass in front of the sensor and the Baader-U filter (320-390nm),
lens used was the UV-Nikkor 4.5/105mm and sunlight as light source.

Roofs of some neighbouring houses showing strong polarizing effect of glass windows and metal:


Thanks Klaus, how did you manage to find a polarizer that transmits UV?
Those I've looked at have practically no transmission, certainly the Variable NDs (two stacked polarizers) have <0.02% at 400nm.

FWIW metallic reflections aren't polarised - at least in the visible - I think it's highly likely the metal round those roof windows is all painted/lacquered (paint does polarize it's reflections)


Thanks for the hint, those may well be painted metal frames indeed!

A fried of mine and I have tested quite a bunch, and I was lucky and found some Zeiss dedicated polarizers for UV, so those work down to 300nm. Later I also found out that some older Heliopan uncoated polarizers (certainly NOT the modern MC coated high transmission ones!) did transmit rather well to about 340nm, and so does some older Zeiss Jena BERNOTAR polarizers, but not as good as the Heliopan ones. The loss is about 2.5-3stops though.



I can see it would be worth my checking all my old polarizers, I might have some that are usable Smile
It's all too easy to jump straight on e-bay at the moment, but I've got enough extras I've remembered a use for on the way already...
I will note those models in case none of my current ones prove suitable. Thanks for the info!


Btw. it cannot be generalized, justed tested about 8 Heliopan filters and only two f them are kinda good for UV, the others are not. Seems to be age related, the older ones performed better for UV! They must have changed the polarizer foil types over the years.


PostPosted: Thu Apr 02, 2020 11:57 pm    Post subject: Re: Polarized Reflected Ultraviolet Photography Reply with quote
kds315* wrote:

Btw. it cannot be generalized, just tested about 8 Heliopan filters and only two f them are kinda good for UV, the others are not. Seems to be age related, the older ones performed better for UV! They must have changed the polarizer foil types over the years.

I suspect the coating might have a lot to do with it. Standard anti-reflective coatings seem quite good at blocking UV.
A few of my filters will be quite old & I have some bits of unmounted polarizing film too, so I've probably got more options for the polarizing filter than I have for UV transmitting lenses...


PostPosted: Fri Apr 03, 2020 12:53 am    Post subject: Reply with quote
Another dimension for creativity! Bravo!

Alternately, instead of moving filter position sequence move uv source around subject. Insread of sequencing can also stack. Smile


PostPosted: Sun Apr 05, 2020 1:23 pm    Post subject: Reply with quote
Thanks guys!

well here today a bit more about it, using a PHLOX - Rockfoil flower and a deep reaching (up to 320nm) circular polarizer in front of a Baader UV filter (320-390nm)

Phlox flower in M-mode i.e. non exposure compensated:



Phlox flower in A-mode i.e. exposure compensated:



PostPosted: Tue Apr 07, 2020 1:35 pm    Post subject: Reply with quote
Here another example (white Saxifraga flowers), which shows the predicted effect my friend told me about: That bees have around their eyes sensors able to detect polarized light and there woud be flowers using that:

Visible Light - Sunlight:




Reflected polarized UV, only sunlight:




Reflected polarized UV, using a 365nm UV LED:



PostPosted: Sat Apr 11, 2020 2:46 pm    Post subject: Reply with quote
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):



PostPosted: Wed Apr 15, 2020 12:24 pm    Post subject: Reply with quote
So today about Lewisia - Cliffmaids in reflected and polarized light



PostPosted: Sun Apr 19, 2020 6:45 pm    Post subject: Reply with quote
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



PostPosted: Tue Apr 21, 2020 10:45 pm    Post subject: Reply with quote
Different approach used here, delivers more intense colors...



PostPosted: Mon Apr 27, 2020 3:30 pm    Post subject: Reply with quote
Gazania rigens in polarized reflected UV light



PostPosted: Mon Apr 27, 2020 5:26 pm    Post subject: Reply with quote
Like 1 Like 1 Nice one!


PostPosted: Mon Apr 27, 2020 7:42 pm    Post subject: Reply with quote
Thanks for sharing, this is quite hypnotizing Laugh 1


PostPosted: Mon Apr 27, 2020 8:30 pm    Post subject: Reply with quote
Thanks guys, I find this gif-thingy quite nice myself! Wink


PostPosted: Tue Apr 28, 2020 6:17 am    Post subject: Reply with quote
Nice to see your polarization experiment. Obviously I was not familiar at all with utilizing specular reflection along these lines to create a polarized picture. So that was an intriguing piece of logical history to find out about.
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