Any effective polarized lenses will have a light transmission of no
greater than 50%. That's because they're filtering the horizontal
component of the light. Some manufacturers claim 50% transmission, but I
don't believe it, or if it's true then the polarization is poor. It's
theoretically possible with perfectly polarizing neutral gray lenses,
but not with lenses with any color tint. (That's because the tint would
also filter some of the spectrum of the vertical component.) In
practice, I suspect the best you can hope for is around 30% light
transmission, and even then I doubt that the polarization would be as
effective as is possible with darker lenses.

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