I just realized that no one ever answered the question about using these at night...! For the life of me, I can't figure out what benefit they would serve to using them at night. And this includes polarizers too. I may very well be wrong about this, but if the purpose of them is to filter out UV.... and there's no sun..... what are they filtering? I may be very wrong, but is there uv light at night? Now I'm curious. Maybe you are thinking about the flourescent or phosphourous lights that often turn images green.....? They do make filters for that too which will basically filter out the light and give the correct balance..... but that's what the built in white balance in your camera is for.

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