Linear and Circular Polarizer

[Steve Smith]

I'm not sure about circular being more subtle. The first part of a circular polariser is an ordinary linear polariser. The extra bit is a layer which randomly rotates the already polarised light.


Steve.

[George Collier]

I have heard (read in these forums) before that linear polarisers are more dramatic, or pronounced, in their effect.
I see two disagreeing posts in this thread on this, although neither one seems certain.
All of mine are linear, but I may in the future have a camera that needs a circular one. Does anyone know for sure?

[Steve Smith]

I can't see how the polarising part of a circular polariser can be any less effective than a standard linear polariser (because that's what it is). However, it might be possible that the re-circulificating* bit is somehow reducing the contrast a slightly making people think it's less effective at polarising.

(* I can't think of the right word).


Steve.

[Jeff Kubach]

I use a linear on my RB67.

Jeff

[cliveh]

I am a little confused with this thread. Am I correct in thinking that the circular polarising filter is merely two linear polarising filters mounted together, where one rotates?

[Steve Smith]

No. It's a single linear polariser with another layer which puts the light back in a random orientation so cameras with lightmeters and/or AF which use polarisers internally will still work.


Steve.

[AgX]

which puts the light back in a random orientation

No, but circular polarisation mean a steady uniform variation of polarisation. "Random orientation" is what characterises un-polarized light.

[bsdunek]

I can't see how the polarising part of a circular polariser can be any less effective than a standard linear polariser (because that's what it is). However, it might be possible that the re-circulificating* bit is somehow reducing the contrast a slightly making people think it's less effective at polarising.

(* I can't think of the right word).


Steve.

You may have hit it. It could be the contrast difference.

[Jim Rice]

All I can tell is from my experience. I had a B+W linear which was easy to see the effects of on the viewing screen and in the transparencies. I recently acquired a Contax circular the effect of which is much more subtle (to the point that I can usually not find the correct angle using the finder.) Perhaps my linear was great (it was) and the Contax is a dud.

[sbuczkowski]

RE #15: No. A circular polarizer is a linear polarizer followed by a 1/4-wave retarder plate. The linear polarizer does the polarizing (really it just selectively admits light with a polarization axis aligned with the polarizer and rejects anything else. it doesn't create any polarization). The light after this part is linearly polarized and it is this that can cause problems with meters and AF systems. So, the circ. polarizer puts the 1/4 retarder next which turns the linear polarized light into circularly polarized light which doesn't cause problems in metering and AF.

steven