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Old February 28th, 2006, 06:12 PM   #1
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HD100 and Circular Polarizer Filter (at night)

Anyone use a Circular Polarizer Filter with the HD100? how about at night?

The director [of this project i'm working on] ordered a circular polarizer filter on ebay. I didn't plan on using filters for the camera, but I know that polarizers usually help reduce reflections in glass and stuff.

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Old February 28th, 2006, 06:52 PM   #2
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You will lose about 2 and 1/3 stops with a polarizer.
I generally stay away from circular polarizers because they are basically (always on) and you can't rotate them to control the effect of polarization.
However, they will work at night to reduce reflections on glass, but the light-loss might not be worth it.

BTW, I've moving this into the "Photon Management" forum where we discuss lighting and camera technique.
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Old March 1st, 2006, 11:02 AM   #3
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crap. any other suggestions on reflection-removal? i've read about a Krylon product that dulls reflective surfaces temporarily and you just wash it off.

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Old March 1st, 2006, 12:34 PM   #4
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Quote:
Originally Posted by Tim Dashwood
I generally stay away from circular polarizers because they are basically (always on) and you can't rotate them to control the effect of polarization.
Sorry Tim, that's not quite right. A circular polarizer does indeed rotate to control the direction of polarization. In fact, a circular polarizer consists of a linear polarizer as the first stage of the filter. What is different is that a circular polarizer has a second stage consisting of a quarter-wave plate that, in effect, makes the polarized light more compatible with light-dividing optics used in auto focus and auto exposure systems. (The two-stage construction is also what makes circular polarizers more expensive.)

However, there is certainly a lot of debate over which one is better and/or produces more polarizing effect on certain cameras, which is why one should try both on their camera to find out. The HD100 has a beam-splitter for the three CCDs, so it may be that it will negate some of the polarizing effect. (I haven't tried a circular polarizer on a 3 CCD camera yet to know for sure.) But in general terms, a circular polarizer certainly does the same thing as a linear one.
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Old March 1st, 2006, 12:48 PM   #5
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Tim,

I've always stayed away from circular pola's myself, simply because they are unnecessary for motion picture and video shooting (the still guys use them). I've also found it frustrating that they are most commonly recommended by camera shops to DV users because they cost more, not because the user needs them, which is a straight-up racket.

But in any event, I believe they are operationally identical to linear polarizers, it's just that the back side contains a retarder that de-polarizes the light (but retains the effect of the initial polarization).

The classic compensation is 1 2/3" of a stop, although I've always used 2 stops to be safe. There are 1 stop polarizers available which have less of an effect but are a good compromise for low-light work. And it's worth spending the extra money on the late model versions such as the Schneider True-Pol and the Tiffen Ultra-Pol, because they offer a greater effect than others.

Efrain, having a can of Dulling Spray is a good choice for little kicks and things around the set. For other reflections, setting flags to knock down the reflections may be possible. It all depends on the specific situation.
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Old March 1st, 2006, 12:51 PM   #6
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Got there ahead of me Earl, good job. I will add that I've used linear polarizers on beam-split 3 CCD cameras for many years and they work as expected. I believe the beam-split problems occur with auto focus and metering as found in still cameras, but not with the process of imaging as with video cameras.
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