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Old November 20th, 2005, 12:39 AM   #1
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Circular or linear polarizer?

It amazes me that after umpteen years I've not tested this but... since I've always had SLR's with off-the-film metering (Pentax LX hammer, doubles as a camera) and thus have always used circular polarizers for exposure's sake, does it make any difference on 3-CCD camcorders? I've only bought CPs because of this (safer then sorrier).

I know a prism or mirror of sorts splits the colors appropriately, but could a linear polarizer have any effect? Next spring, Zotz notwithstanding, I intend to get an XL-2, as well as move to a 4x4 filter system. Taking notes, now, of course. Autofocus, unless strides have been made in this area commensurate with other aspects of video, is of little importance. Nevertheless, there could be times when it might be used, so I shouldn't have to worry about filtration bonking it. Ultimately, I'll not be penny-wise and pound-foolish, yet there's that side of me that fairly cries out for a reasonable savings.

So, LP or CP with 3 CCDs?
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Old November 20th, 2005, 08:55 AM   #2
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Good Morning, Doug.

Most manufacturers recommend the Circular. I have used both. I can not say that I personally observed any difference. But, when using a linear filter, I can see where under tough lighting conditions, that the image passing through the filter, could be deteriorated before it is on the media.

Why take a chance?
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Old November 20th, 2005, 12:12 PM   #3
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This is a matter of long debate (try doing a search under "circular polarizer" and you'll see the results). Robert, is it that the manufacturers recommend circular polas or the sellers? If manufacturers, where are they listing those recommendations? I have long believed that the sellers have promoted them because they cost more. The filter manufacturers do not specifically spec them for video cameras.

Personally, I have always used linear polas for video and never experienced any problems.
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Old November 23rd, 2005, 07:54 AM   #4
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Charles, you are correct regarding sellers pushing the circular polarizers, and there are as many opinions on this as there are people to ask. We did a rather lengthy test when we first went digital in '99. Linear polarizers worked fine, so did the circular. Only difference? Circular was adjustable, linear wasn't. I like the adjustability of the circular so that's what I use. But, we still have the linear ones around here somewhere.

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Old November 23rd, 2005, 09:20 AM   #5
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Robert, by "adjustable" you mean...?

Obviously both types are "activated" by being rotated to dial in the degree of polarization, not sure what other adjustment there is to a Pola.
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Old November 23rd, 2005, 09:51 AM   #6
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Charles, Yes, my post made very little sense. I apologize-I was interrupted in the middle of writing it. Lost my train of thought. Let's try again and, if my understandig of this subject has been wrong all along please advise.

On our first digicams I had no way of knowing if the optics had polarization employed internally. If so, the linear would possibly have caused too much absorbtion, at least in some cases. The circular would alleviate the issue, if internal polarization was used in the optics, and I never had to worry about it again.
I do not take claim for figuring this out. This stuff came from a Tiffen tech guy that I talked to. As I recall, he felt the whole issue was probably directed more at the digital still cameras, not so much video.

I hope that makes more sense.

Robert
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Old November 23rd, 2005, 10:58 AM   #7
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To my knowledge linear polfilter doesn´t work properly with autofocus, circular does.
anyway, polfilters are not run´n gun, adjusting the pol and manual focus, it´s a non issue

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Old November 23rd, 2005, 12:03 PM   #8
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Alex, your post jogged my memory a bit. I think I might, maybe, recall that was the issue when the Tiffen guy said it was more an issue with still cameras as opposed to the video cams. I do not remember if we tested that. Probably not as we rarely do run 'n gun shooting so, you're right....non issue.

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Old December 9th, 2005, 09:03 AM   #9
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Here's some information on linear vs. circular polarizers from Popular Photography:

"A linear polarizer filters diffused light in unidirectional lines, and can work with most cameras. A circular polarizer consists of a standard linear polarizer plus a quarter-wave retarder that scrambles polarized light so it moves in a spiral or circular direction. A circular polarizer is needed when using many modern SLRs to prevent interference with their polarized autofocusing and autoexposure systems." (Help! - October 2003)

"A circular polarizer works with any camera, whether its metering system incorporates a semi-silvered mirror (in effect, a polarizer) in its light path or not. So if you have a circular polarizer that fits your lenses, you don’t need to buy a linear polarizer. However, it doesn’t work the other way around—if you use a linear polarizer on a camera requiring a circular polarizer, your exposure system may perform erratically." (Tech Support 07/04)

"Virtually any camera with an autofocus system, and many cameras with TTL-metering systems, require a circular polarizer. Using a linear polarizer can result in focusing and exposure errors." (4 Filters Every Photographer Must Own)
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