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Dont understand circular polariser!


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I have a hoya circular polariser, it has a white mark on it for reference of

where it was.

 

Now I keep reading they work best at 90 degree angle to the sun, forgive me if

Im being stupid but I just dont understand this. Does this mean the line has to

line up with the sun at a 90 degree angle or the cameras position? Ive read

about it but I just dont understand what is meant by the 90 degree or at least

its confused me to how you can get a 90 degree angle when the sun, does this

mean if the sun is say high in the north east, then the line has to be 90

degrees right?

 

Im confused. Do you even need to know the angle? Cant you just move the filter

around at look what does the effect best?

 

thanks

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"Now I keep reading they work best at 90 degree angle to the sun..."

 

The sky is polarized most strongly in a band centered at 90 degrees to the sun. A polarizer will have the greatest darkening effect in this region. Whether darker is always "better" is questionable.

 

Light from any non-metallic surface tends to be polarized. Therefore a polarizing filter can remove reflections from water, glass, foliage and rocks, increasing the color saturation of the latter. This is arguably the best use of a polarizer.

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Forget about all this 'degree' geometry stuff. Most of us failed geometry for christ sakes. Just turn the dial until the white mark is about 1/4 of the way down clockwise. Make sure that the Sun is at your side not infront or back of the scene you are trying to take. If 1/4 turn doesn't work, turn it clockwise another 1/4 turn until the white mark is at the half-way point. Good Luck !
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Your camera does not know about any filter on the lens, but you do. Auto white balance, if your camera has it, could add own interpretation. Using manual white balance could give you more predictable results. You just need to try what works best for your expectations.
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We have been here before. Light directly from the sun is considered a point light source, that is, it consists of light rays alligned in parallel. When these rays strike almost any object, they become diffused. The polarizer, any polarizer, is designed to pass only those light rays in a parallel allingment and reject those that have become diffused. This then, eliminates the diffusion that not only will reduce the clairity of the recorded image, but will also allow stray diffused rays to bounce around within a lens. Because of a lens auto focus system, the filtering of some of the light may diminish the ability of the lens to focus. The circular polarizer overcomes this shortcoming.
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"Because of a lens auto focus system, the filtering of some of the light may diminish the ability of the lens to focus. The circular polarizer overcomes this shortcoming."

 

I should think the maximal 2 2/3 stops of light loss from polarizer use would greatly exceed the diffusion effect of unpolarized light -- would it not?

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