Where is the mark on the polarizer supposed to be?

Started 2 months ago | Questions thread
ThrillaMozilla Veteran Member • Posts: 4,928
Scenario for photographing imperfections in polarizers

Well, I suppose that is one possible scenario: extinction of the sun's reflection on a glass window, or on water. I suppose it's possible under certain, rare conditions, to have a reflection with residual violet or red transmitted by the filter.

The problem is, deviations from Brewster's angle will generally overwhelm any residual transmission of visible light, unless you can arrange the reflection to match Brewster's angle accurately. You can move either the sun or the window. You probably can't move the body of water. You can wait for the sun to be in exactly the right position. So which are you going to move?

In the case of a curved surface, such as a drinking glass or a body of water with ripples, you could move the camera or point it in a different direction. At just the right angle, at one spot in your photo, I suppose you might be able to get a hint of residual violet or red in the reflection--which, of course would be strongly suppressed by almost any camera. I suppose if you are looking down at a lake with ripples reflecting sunlight, you might get a slight hint of residual violet or red.

That's probably a pretty rare case, don't you think? Go to some mountain lakes and try it. Or maybe it could happen with foliage. I doubt it, but I can't say it's completely impossible. I'm having trouble coming up with a credible scenario. I could be convince with a single, strong counterexample, but I've never seen a problem.

I still think you will very rarely, if ever, have to worry about incomplete extinction for visible-light photography.

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