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Old May 14th, 2003, 08:32 AM   #1
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Polarizer filter has a ring that "turns"?!

I finally got around to connecting my Tiffen 72mm Polarizor to my DVX100 yesterday. I must say the footage does look more rich with it, and it DOES cut alot of glare out...although not completly eliminating it.
I noticed a ring on the actual filter itself that turns. I watched the footage closely as I turned it and it seemed to ajust the amount of glare that was visible. Does anyone know how this works. I'm such a newb I didn't even know the Polarizer has such a funtion- I figured it was a solid fixed filter like the UV or Warming filters I have.

Lastly, are polarizers known to cut alot of light. I didn't get a chance to do a back-to-back comparison between the polarizer and the simple Uv filter. Also what conditions are recomended for using a polarizer? Is it ok to shoot indoors with it?...or is it mainly for outdoor shooting?
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Old May 14th, 2003, 08:46 AM   #2
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A polorizer cuts glare and provides colour and contrast enhancement. Helps give a richer colour and contrast to sky and water. Foliage and grass are also effected. It also cuts the light by 1 to 1 1/2 stops , which is a good thing on a sunny day.

You are right, the effect of the filter is controlled by rotating it.

http://www.tiffen.com/BFILT_06_07.htm

The only time a polorizer would be used for indoors shooting is to tame unwanted reflections as it would really cut your available light.
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Old May 14th, 2003, 10:48 AM   #3
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Great- thanks for the info. Now when you say it cuts the light about 1 to 1 1/2 stops is that in terms of F.stop (iris)?

Also, do you know how/why turning it adjusts the reduction of glare on subjects thru the lens?!
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Old May 14th, 2003, 10:59 AM   #4
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Glenn -- from How Polarizers Work:

"Linear polarizing filters use optical materials with crystalline structures aligned in such a way that they readily pass incident light linearly polarized in one direction (we'll call it the passing axis) while strongly absorbing light polarized along the perpendicular direction, or blocking axis. These 2 optical axes always lie 90 apart."

Therefore, turning the filter will adjusts the angles of the passing axis and blocking axis, whenever you're dealing with polarized light such as a reflection from a car's windshield for instance. And yes it is like a one- or one-and-a-half stop neutral density filter. Read the rest of the page linked above for exhaustive info -- and continue the discussion right here. Hope this helps!
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Old May 14th, 2003, 11:40 AM   #5
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Glenn

Take two combs, one behind the other, matched up with the teeth pointing in the same direction. See how much light gets through.

Now turn one gradually so that is perpendicular to the other. See how much light gets through now.

That's broadly how polarisers work.
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