Polarizer in UV test

[Andy Perrin]

I inherited an old "OSAWA 52mm PL ∆" polarizer along with a bunch of other equipment from my sister when she moved to Colorado, and I just tested it in UV. There is a noticeable change in the sky. Prior work on this topic has been done by Jonathan here.

 

Camera: Sony A7S modified for full spectrum

Lens: AF-Nikkor 80mm/2.8

Filters: 1.75mm S8612 + 2mm UG11

Settings: F/2.8 ISO1600 1/8" (aperture wide open),

White balance: in camera, off PTFE without the polarizer on

 

No adjustments to the images besides resizing and lowering the exposure setting by one stop. All three images have the same settings, as verified by copy and pasting them in PhotoNinja.

 

 

No polarizer, exposure reduced in PhotoNinja by 1 stop to make the sky visible

 

With polarizer, rotated to give the darkest image

 

With polarizer, rotated to give the lightest image

 

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I also tested (with same settings and processing as above) a Tiffen polarizer:

 

Rotated to give the darkest image:

 

Rotated to give the lightest image:

 

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Putting all the results together, it seems they perform pretty similarly.

[Stefano]

My 3D goggles simply absorb all UV light, like if they were made of polycarbonate.

[Andy Perrin]

Your goggles probably have cheap plastic polarizers, which are known not to work in UV.

[OlDoinyo]

Most polarizing filters contain a laminated sheet of plastic. I am not aware of any way to polarize glass as such. Some antique polarizers were made out of tourmaline crystals a century or more ago, but they were costly. I am surprised that much UV passes the filters above--I should check mine for transmissivity.

[Andy Perrin]

It's not the glass that's polarized, usually they have some kind of material with tiny rods oriented in the same direction (for ones that aren't plastic sheets I guess).

[Stefano]

The plastic ones should be made of aligned polimers.

[dabateman]

Andy,

What uv filter did you stack the polarizer with?

I am surprised the tiffen worked. There filters seem to just be film between glass plates.

[Andy Perrin]

Andy,

What uv filter did you stack the polarizer with?

I am surprised the tiffen worked. There filters seem to just be film between glass plates.

1.75mm S8612 + 2mm UG11

[DaveO]

Andy,

 

I'm guessing that the older filter was a linear polarizer:

https://en.wikipedia.org/wiki/Polarizing_filter_(photography)

 

so you have inadvertently shown that it really doesn't make any difference with digital sensors whether the filter is linear or circularly polarized but the linear one may upset the focussing of SLRs.

 

Dave

[Namestom]

What would be the purpose of using a polarizer? It seems to cut out alot of detail and any color. I have a tiffen high transmission CPL. I can try it out too. Glass polarizers have layers of coatings that polarize the light.

[Andy Perrin]

What would be the purpose of using a polarizer? It seems to cut out alot of detail and any color. I have a tiffen high transmission CPL. I can try it out too. Glass polarizers have layers of coatings that polarize the light.

To cut reflections! UV photos tend to be highly glossy making it hard to see anything but the reflection in some cases. Take a look at Jonathan's flower photos with and without the crossed polarizers here:

https://www.ultravio...dpost__p__26164

 

Mine was cutting a little of the color but not all of it.