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Identifying axis of a polarizer
To identify the axis of a polarizing filter, make this small experiment.
Hold the polarizer to your eye (with the male thread towards you) when looking at a light source reflected on a horizontal surface (a glass or polished table will do). Rotate the polarizer until the light’s reflection almost disappears.
When the reflected light is at a minimum, your polarizer’s blocking axis will be parallel to the surface (horizontal in our example). It can be a good idea to mark the position of the blocking axis on the edge of the filter.
Once the blocking axis has been identified, using the polarizer is easy.
Generally speaking, to cut the reflections on any horizontal surface (like a lake) simply place the blocking axis horizontally. To cut reflections from a vertical surface, place the blocking axis in a vertical position. Fine-tuning can improve the results. A rotation by 180 degrees (a half-circle) doesn’t change the output; the maximum rotation you will have to apply is 90 degrees.
If you’re not sure of the angle of your reflective surface, or if you don’t have reflective surfaces but want to improve the look of foliage, the sky, you can use your camera to evaluate the correct position for the blocking axis.
Illustrations and text by Bernard Dery
