Near infrared and ultraviolet polarizing filters?

[Avalon]

  Hello. I wonder if there are polarizing filters that work for near infrared and ultraviolet for photo camera's?  And if yes, how useful are they? I could find them useful for example in removing when photographing art works to remove for example varnish reflections. For visible spectrum polarising filters can definitely improve image quality by removing reflections from non metallic surfaces, reduce glare and make sky darker. However when I tested a regular CP filter with a NIR camera I saw no reflections being removed, I assume infrared rays due to their good penetration just passes through unaffected. When I tested with 365nm light the same filter would remove reflections but also partially block UV. There are several types of polarising filters - linear and circular, also I heard INVU glasses use Ultra polarized filters, not sure of marketing trick or actual category of P filters.  

[ulf]

There are a few efficient scientific polarizing filters out there, but they are a bit expensive and often have a small diameter.

Here are a few examples:

https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=4984

https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=752

 

 

A few older linear polarizing filters has been found having at least a marginal effect, but it decays quickly for longer wavelengths.

 

All such filters have a minimum blocking of at least one stop, normally more, if the incoming light is randomly polarized.

The loss then is a combination of surface transmission losses, general material losses and that the polarization cut away half the light.

[Andy Perrin]

Jonathan found some “accidentally good” UV polarizers a few years ago. At the time he didn’t want to disclose that info, but you could aways ask him. His reasons for not disclosing it may be moot by now. 

[JMC]

I tried some different (older) linear polarizers, and found a few which were ok for 365nm at least. Never tried them for IR. From memory, i think AICO ones were one of the ones that were ok for long wavelength UV, but quite a few old linear polarizers were ok.

 

Of course if you have won the lottery, these are pretty good - https://moxtek.com/optics-product/ultraviolet-polarizers/

 

 

[Avalon]

I read in blog one guy used a full spectrum modified camera to capture infrared photos with a Hoya CP filter and it worked. Not sure how much his IR filter passes visible, shorter wavelengths. My filter is 930 nm. I wonder how well that filter would work for UV, if multicoated it may have ultraviolet blocking coatings. Here is the link to the blog: https://www.dimagemaker.com/using-circular-polarizing-filters-for-digital-infrared-photography/

[dabateman]

I found some accidentally UV polarizers. I also may still have a sheet of linear polarizer,  intended for making 3D glasses, that also worked to polarize IR. But its all hit and miss with regular photography filters.

If you really want UV or an IR polarizer,  they are expensive. 

 

[ulf]

2 minutes ago, dabateman said:

I found some accidentally UV polarizers. I also may still have a sheet of linear polarizer,  intended for making 3D glasses, that also worked to polarize IR. But its all hit and miss with regular photography filters.

If you really want UV or an IR polarizer,  they are expensive. 

 

How well they work for IR depends very much on the wavelength. 

For a 930nm filtered image this becomes very difficult and the effects will likely be very marginal if the polarizer is not designed for that wavelength.

If you can find a big heap of old polarizers very cheaply you might find some that have some effect among them. 

[Andy Perrin]

I got a NIR polarizer on eBay one time for relatively cheap. 

[ulf]

3 minutes ago, Andy Perrin said:

I got a NIR polarizer on eBay one time for relatively cheap. 

Yes, sometimes there are bargains to be found there if you have some luck.

Was it a small diameter filter?

[ulf]

Scientific polarizers are often used for laser optics and if there has been high power involved they might be partially defect due to overload

[Andy Perrin]

12 hours ago, ulf said:

Yes, sometimes there are bargains to be found there if you have some luck.

Was it a small diameter filter?

25mm, yes.

EDIT: Consulting the ebay receipt shows it was actually 20mm. 

[Avalon]

11 hours ago, Andy Perrin said:

I got a NIR polarizer on eBay one time for relatively cheap. 

 

Can you provide a link to the near infrared polarizer you found on Ebay or seller name? How well does it perform in UV? I have tested grandfather's soviet era polarizer filter but it doesn't work in the NIR spectrum as well. Going to test now Hoya polarising filter Pro1 Digital 52mm with multi coatings..

[Andy Perrin]

It was in Jan 2020, and the seller was “cl2005”. The item was:

Melles Griot Near-IR Metallic Thin Film Polarizer 03FPI003, 780-1250nm

I paid $50 plus shipping. 

 

I have never tested it in UV because that’s not what it was designed for. (Why would you expect it to even work there??)

——

I actually see one for sale on ebay now for $200. Seller is “galacticmarketplace”.

[Avalon]

Thanks, I will look into it. I today I bought a cheap used Hoya polarizer pro1 digital 52mm filter with multi coatings (original) and tested it. So with 930 nm there is barely noticeable reflection removal. Then I tried using full spectrum modified phone with 720nm filter if I remember correctly and there is much more noticeable reflection removal but as dramatic in visible spectrum, here I used glossy black plastic lid to demonstrate polariser filter effects, sorry about poor quality of unprocessed photos, phone camera has no focus mechanism: 

As for UV, this filter removes reflections from glass tiles much better than in the NIR spectrum and surprisingly doesn't block UV so strongly as Chinese CPL filter. Strange thing is that the uncoated chinese filter is more transparent that Hoya multi coated filter in the visible spectrum. Red tinted photos were made using 365nm radiation and UV only pass filters: