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On 15/08/2020 at 16:31, wiskerke said:

Then there is this image of a (probably cheap) UV filter:

UV filters test - supplement - Introduction

translated https://www.lenstip.com/120.1-article-UV_filters_test_-_supplement_Introduction.html

from a well known Polish photography site https://www.optyczne.pl/

 

It's been disputed what we're seeing here, but whatever it is, it's totally not even:

  From https://www.lensrentals.com/blog/2017/06/the-comprehensive-ranking-of-the-major-uv-filters-on-the-market/

  Brandon Dube - Chris Jankowski 3 years ago

  In the second link (120...) they claim they've captured interference fringes. They most assuredly have not -- there is no type of interferometer (Fizeau, white light, michelson, lateral shearing, etc) that produces such sharp fringes with that large of a spacing.

  Their spectral transmission charts are difficult to comprehend, as is their notation for extinction coefficient. IMO.

 

Assuming you are referring to the interferogram shown, I agree it is unusual and couldn't be caused by simple optical non-flatness or variations in thickness for exactly the reason you say. But if the UV filter is made from polymer film sandwiched in adhesive between two glass flat sheets, and the polymer is also optically active then I think it's possible to get all sorts of wierd effects. I remember being involved in some work on polarizing filters in the coherent light path of an interferometer and we saw all sorts of effects. If I recall correctly the problem we had was that some of the interference coherence was disrupted within the plastic film and the effect was temperature sensitive. It might be interesting to know how the filter concerned was made. Multilayer vacuum deposited coating or sandwiched polymer?

 

Mark

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9 hours ago, M.Chapman said:

 

Assuming you are referring to the interferogram shown, I agree it is unusual and couldn't be caused by simple optical non-flatness or variations in thickness for exactly the reason you say. But if the UV filter is made from polymer film sandwiched in adhesive between two glass flat sheets, and the polymer is also optically active then I think it's possible to get all sorts of wierd effects. I remember being involved in some work on polarizing filters in the coherent light path of an interferometer and we saw all sorts of effects. If I recall correctly the problem we had was that some of the interference coherence was disrupted within the plastic film and the effect was temperature sensitive. It might be interesting to know how the filter concerned was made. Multilayer vacuum deposited coating or sandwiched polymer?

 

Mark

 

Which would mean we should be able to see it with a pola filter and polarized light.

 

wim

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Gee, I would have guessed it was caused by Cosmic rays being blasted at us from one of the moons of Jupiter by an alien race in order to make us all crazy and therefore a cinch to conquer when they finally show up.  Their evil plan seems to be working so far.  I would suggest tin foil hats for everyone and the camera/lens.😁

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4 hours ago, Johnnie5 said:

Gee, I would have guessed it was caused by Cosmic rays being blasted at us from one of the moons of Jupiter by an alien race in order to make us all crazy and therefore a cinch to conquer when they finally show up.  Their evil plan seems to be working so far.  I would suggest tin foil hats for everyone and the camera/lens.😁

 

Haha!

Maybe they're from the same people that brought us these:

Mad Ad Men: X-Ray vision

Or they're from the Twilight Zone....

 

wim

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