Where is the mark on the polarizer supposed to be?

Started 2 months ago | Questions thread
OP Dem Bell Regular Member • Posts: 330
Re: Where is the mark on the polarizer supposed to be?
2

dsjtecserv wrote:

Thus, as Thrilla said, the angle that matters is the angle of incidence at the surface, but since it won't be the same as it (always) is for the sky, the handle or indicator mark would not be accurate anyway. I don't know if that explains the discrepancies you see,

No, it does not. The fact that the glass was not firmly fixed in the frame and probably was forced out of its original orientation is the most likely answer.

but it probably isn't worth trying to make the mark work for non-sky situations!

We should separate the physical properties of the filter (which can be marked or not marked on its body) from how the filter might be used (which has no effect on the physical properties of the filter and its markings).

A polarizer has a transmission axis that lets through all light components parallel to this direction and blocks all light components oriented in the perpendicular direction. These are physical properties of the polarizer determined by the anisotropic structure of its optics - think thin parallel metal wires running through the glass. Whether the polarizer sits in the bag or is used to darken the sky or to remove reflections - this does not change the fact that these thin wires still run parallel to each other along a certain direction. The manufacture can choose several options how to mark this direction (minimum effect) or the direction perpendicular to it (maximum effect) on the photographic filter:

  • don't have any marks at all (by far the most common option nowadays)
  • put a mark on one side of the filter (that's what Hoya and Marumi do for the "maximum effect" direction)
  • put two marks on opposite sides of the filter to show the axis (this would have been a sensible option that reflects the symmetry of the polarizer, but I don't think anyone does that for photographic filters)
  • mark both "maximum" and "minimum" directions that are at 90 degrees to each other (I don't think anyone does that either)

It is interesting to see how polarizers evolved. First, there were marks and even handles (because it makes sense to have one) but then manufactures seem to have given up on the idea (probably because most people did not use the marks anyway).

Going back to how to align the polarizer to get rid of reflections. If the reflection is from a vertical surface, like a window - the mark should point vertically. If the reflection is from a horizontal surface, like water in a pond - the mark should point horizontally. Of course, no one needs to know this to be able to use a polarizer, especially when it has no markings on it...

One more thought. If I wanted to place company's logo in the most visible place on the polarizer, I would put it close to where the "maximum effect" mark should be. Then the chances are the logo will stay close to the top of the lens for everyone to see it.

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