Blue yellow polarisers, how do they work?

[l2oBiN]

Could anyone explain how these actually work? How do they assign color?

[polyglot]

I am not certain of the exact process but I believe it relates to wavelength-specific operation of the quarter-wave plate seen in a circular polarizer. Green light through a CPL will come out circularly polarized but blue or red light will come out with a bias to one axis (an elliptical form). I suspect that there is a second polarizer after the first to detect this effect.

While I'm pretty sure that the physics of it relates to that (wavelength-dependent performance of the QWP), that arrangement I describe above doesn't explain the full effect of these filters.

The quarter wave plate may also be a 3/4 or 5/4 plate, which would give a much stronger colour effect. I suspect the filters involve a rotation between the front polarizer and the wave plate (second polarizer perhaps fixed to wave plate) but I'm totally not certain about that.

[ki6mf]

Think of a color filter as passing one color and blocking other colors. Green and Red as an example Green will make green subjects lighter and Red Subjects darker. Yellow is used to make the sky appear "normal" in Black and White film. Color filters are sometimes used to make a scene "warmer". As the quotes indicate this is somewhat subjective and personal taste comes into play.

[l2oBiN]

Perhaps polyglot was on the right track? Anyone with more info?