Sounds crazy, but I’m having trouble with a Circular Polirizer Filter. Actually it is the 3rd one the manufactor sent me. And they all seems not to work properly.
When I mout it to my camera (Sony PDW-F800 / XDCAM 422), if I rotate it, I get only a little change in color. But when I hold it in front of my lenses inverted, with the screw outside, I get exactly what I would expect from a Polirizer filter.
I’ve learned that a good way to test a CPF is to put it in front of a LCD TV or display. The LCD emits polirized light, usually in 45 degres. So the filter would affect how you see the LCD.
I did ecxactly that and I got a little color change when placing it correctly in front of the LCD. But I got what I expected when I holded it inverted.
Took some pictures…
I assumed it was mounted inverted in the manufacturing process. But 3 of them?
Any ideas?

Thank you very much for your help!