 Glenn Theal |
Rotation of a Circular Polarizer Hi, I just wanted to double check something that I know is an issue with linear polarizers. Will rotation of a circular polarizer affect the degree of polarization that occurs before light reaches a lens? I've noticed that rotating a circular polarizer does seem to change the degree of colour saturation of the sky when I'm looking through the view finder. However, I want to confirm that this is not just the result of changing lighting conditions in the environment. If the answer to this quesiton is yes, then how can I most easily tell the degree of roation that offers the least and most polarization? Cheers,
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Jeff S. Kennedy |
Yes, rotating the polarizer affects the amount of polarization (not the amount of light). You should be able to see the effect through the viewfinder. Remember that the effect is strongest at 90 degrees to the sun. At other angles it may be more difficult to see the change. You can tell before you mount it on your lens whether it will be effective by holding it in front of your eye and rotating it.
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John A. Lind |
Glenn, In addition to what Jeff has mentioned, a little technical information about what circular polarizers are and how they work: A circular polarizer is a linear polarizer with a "quarter wave plate" added to the back side. They are cemented together so you can't see the two separate pieces. The linear in front has the same effect as a pure "linear polarizer" and this is why you see its effect as you rotate the circular polarizer. The 1/4-wave plate on the back side circularly polarizes all the light *after* it passes through the linear, so your camera metering and AF system won't get fouled up by pure linearly polarized light. This does not change the visual effect the linear has on light passing through it first (why it works). Light Path: -- John
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Glenn Theal |
Thank you, both! I appreciate the feedback, and the explanations were wonderful. John, thank you, especially for providing the technical info on the circular polarizer. Cheers,
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