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Circular polarizing filters

manappraisal's picture
Last seen: 6 years 9 months ago
Joined: 11/11/2007 - 3:35am

I am new to the world of filters. I just purchased a Hoya circluar polariziing filter and will be testing soon.

My impression is that the filter is supposed to be adjustable via the free turning outer ring. However, when place to my eye and turned, nothing happens. The outer ring turns freely, but no adjustment on the brightness occurs. Is this normal? If so, then what does the outer ring do, if it does not vary the amount of light which passes through. This experiment was done in bright sun light.

Thanks.

Jeff Deuitch

Palmetto, Fl



birdcat's picture
Last seen: 1 year 11 months ago
Joined: 10/21/2005 - 10:09am
Plus Member Moderator

Try pointing the camera (with the filter on) at a reflection in a pane of glass (say at a 45 degree angle), then turn the ring and see what happens. If you don't see a drastic difference (the reflection disappearing and what's behind the glass showing through), then you don't have a polarizing filter or you're doing something (like the mounting) drastically wrong.

Perhaps you're wanting a neutral density filter?

Bruce Paul 7Squared Productions http://www.7squared.com


manappraisal's picture
Last seen: 6 years 9 months ago
Joined: 11/11/2007 - 3:35am

No, definitely want a ploarizing filter.

Perhaps they work differently than the polarized glass we used to play with back in physics. Withthese, light was only allowed to enter in a single plane. If you put two pieces togetherin the same orientation, light was largely unaffected. If you turned one of them 90 degrees, then one blocked out all the 'vertical" light and the other would block out all the "horizontal"light. The nbet result was that no light passedthrough. I thought that perhaps a polarizing filter would work thesame way. I did see a Youtubevideo where a guy had a circlar polarizing filter and demo'ed it with exactly the same results I am describing. This is why I am a bit perplexed that the Hoya filter I purchased does not seem to do this. It has the free truningring in the front, but when looking through the filter by eye and turn the front ring, there is no perceptable difference. It is definitely labeled as a polarizing filter.

Thanks.

Jeff

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Try pointing the camera (with the filter on) at a reflection in a pane of glass (say at a 45 degree angle), then turn the ring and see what happens. If you don't see a drastic difference (the reflection disappearing and what's behind the glass showing through), then you don't have a polarizing filter or you're doing something (like the mounting) drastically wrong.

Perhaps you're wanting a neutral density filter?

<p class="poststuff">Posted 1 hour ago # PM This User


birdcat's picture
Last seen: 1 year 11 months ago
Joined: 10/21/2005 - 10:09am
Plus Member Moderator

You will get some light reduction but not to the extreme (like a stronger ND filter), however you should notice something when the filters are at opposing angles. Hoya is a name brand so I don't think that's your problem. If the filter is mounted correctly you should see something - I'm stumped.

Bruce Paul 7Squared Productions http://www.7squared.com


D0n
D0n's picture
Last seen: 2 months 2 weeks ago
Joined: 11/09/2007 - 5:28pm

did the thought occur to you that maybe the youtube clip you saw had used TWO polarizers? one on camera to exaggerate the effect, and the one you saw in the clip?

the variable nd effect works best with two linear polarizers or one linear and one circular...

to see the effects of a polarizer easily... point it up at blue sky 45 deg from the sun, then rotate it...


manappraisal's picture
Last seen: 6 years 9 months ago
Joined: 11/11/2007 - 3:35am

You know, I did not think about that. It might be possible. However, the person in the video seem to be describing the use of a single filter. I will go back and review.

Thanks for the advice. I am in a learning curve with respect to filters.

Regards.

Jeff Deuitch

did the thought occur to you that maybe the youtube clip you saw had used TWO polarizers? one on camera to exaggerate the effect, and the one you saw in the clip?

the variable nd effect works best with two linear polarizers or one linear and one circular...

to see the effects of a polarizer easily... point it up at blue sky 45 deg from the sun, then rotate it...