why does my circular polarizer rotate

I think he means, "Why, if rotating my circular polarizer filter does nothing, did they manufacture it with rotation capability?"

I guess it's because you could add a grad filter on top of it, and you might want to have THAT rotate. Maybe?
 
Not following you. You have to rotate a polarizer in order for it to exude its effect. Whether it's "circular" or "linear" has nothing to do with the necessity of rotating it to optimal position.
 
Mine rotates so I can make the clear blue sky appear dramaticaly darker and bluer under some conditions. It can also to help reduce reflected polarized light when desired. One example would be to help visualize the occupants of a car through a car window.
Rotating the filter is how it is adjusted, or aligned, to block polarized light.
 
Oh - DOH! Until seeing those last two posts, I didn't realize my post could be taken as being a jerk... sorry, didn't mean to come across that way. I thought the question was somehow related to "why does a circular polarizer rotate, shouldn't it not rotate because it's circular" or something like that.

Yes, Soliton laid out the reason as to why you would want to rotate one. I was just saying that they all rotate because I thought you were getting at the idea that you thought it didn't have to. I was just reassuring that all polarizers are supposed to rotate, that's how they work.

But I could have gone further. Didn't mean to come off as a jerk!
 
wjm said:
I think he means, "Why, if rotating my circular polarizer filter does nothing, did they manufacture it with rotation capability?"
Click to expand...
Ah, I have now engaged my apparently-previously-disconnected brain.

Rotating a polarizer does everything -- they don't just rotate, but instead you have to rotate it in order to find its orientation of most effect.

I guess it's because you could add a grad filter on top of it, and you might want to have THAT rotate. Maybe?
Click to expand...
No, it's because depending on where the light is coming from, a polarizer will have varying effectiveness depending on what position it's rotated to. Under some conditions it may have minimal effectiveness, but as you rotate it you can see the polarization effect getting stronger and stronger.
 
Barry, I really doubt anyone thought you were being a jerk but, rather, probably just trying to up your number of postings.

lol
 
Polarizers work by only allowing certain wavelengths of light to pass through and reflecting all others. But light travels in 360 degree planes, one orientation will eliminate some wavelengths and another orientation will eliminate others, to optimize the effects you have to be able to rotate.
 
I tried rotating it today and wow. I didnt think it would make such a big diffrence but rotating it is what makes it work.
 
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