Blackmagic Forum

Circular Circular Polarizer VS Rectangular Circular Polarizer

Ok so that may be a mouthful, but in reality I am a bit confused.

I have been using circular circular polarizers for many years, but just recently bought the rectangular kind.

I set it inside the mattebox and expected it to work normally, by polarizing light according to the angle it is rotated.

It did not.

No matter how I rotated the mattebox, this rectangular circular pola did not show any effect, except for the 1.5 stops of light loss, of course. And a slight green/magenta tint.

Am I missing something?

Why is this rectangular kind even created and how it is supposed to be working?

Thanks for any advice.

Emilian Dechev wrote:Why is this rectangular kind even created and how it is supposed to be working?

This 2019 ASC article should answer your questions:

Understanding Polarizing Filters
https://theasc.com/blog/shot-craft/unde ... ng-filters

Emilian Dechev wrote:I have been using circular circular polarizers for many years, but just recently bought the rectangular kind.

If your camera doesn't require a circular polariser, linear polarisers are less expensive. Second hand, they can be dirt cheap. Because people don't know any better, nobody wants them anymore. As a user of the Lee100 filter system, I was able to purchase a 100mm x 100mm Lee linear polariser from a major online retailer, second hand, for US$30. Lee no longer makes this. For the Lee100 system, Lee sells a round circular polariser for which it charges US$310.

Thank you for this article, but I think you mis-understood the topic.

I am not asking anything about "linear polarizers".

I am asking about the "rectangular circular" polarizer, or in other words it is just a "circular polarizer" made in a rectangular shape.

I cannot get any effect out of it, no matter how much I rotate it.

The article discusses both kinds and how to use them.

Aaaaah now I got it!

I just had to turn the filter around. So when you have a "single polarizer" the orientation matters.

Its all good now

Emilian Dechev wrote:Thank you for this article, but I think you mis-understood the topic.

... it is just a "circular polarizer" made in a rectangular shape.

I cannot get any effect out of it, no matter how much I rotate it.

Emilian Dechev wrote:Aaaaah now I got it!

I just had to turn the filter around. So when you have a "single polarizer" the orientation matters.

Its all good now

Yes, the ASC article has an entire paragraph on this, which is why I suggested you read it:

If you’re using a circular polarizer, it’s crucial that you secure the filter with the wave-retarder facing the lens; if you place the circular polarizer backwards, it will have no polarizing effect at all. If it’s a round-shaped circular polarizer with threading, then the manufacturer has already oriented the filter correctly for you — it can only connect to the lens in one direction. A non-threaded filter, however, can be oriented either way. There should be a marking on the filter to the effect of “this side out.” Pay attention to that instruction! That labeling also makes for an easy way to tell if a polarizer is circular or linear.