Polarizing Filters

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Polarizing Filters

Postposted on Thu Apr 01, 2010 11:20 am

So after seeing Lex-ington mess around with polarizing filters and reading about the polarizer's purpose, I found myself rummaging through the never ending photography supplies at this pawn shop again. This time I ran across a few 49mm polarizers and I figured "Ehhh, what the hell is $5.00". So I bought them since they were apparently in good shape, one of which seemed to be pretty much new. I grabbed a Ambico R-8945. I noticed how the portion of the lens that you can rotate had a smoothness to its rotation (almost like a camera focus ring with ball bearings). I also grabbed a Hoya 25A, which I later saw was supposed to be meant for B&W photography, but ehh... who knows I might use it.

Well I went home to see what I had gotten by google searching and I came across an article regarding Circular Polarizers vs Linear. Considering both of these just say Polarizer and nothing about circular, It looks as though I've got just plain old polarizers. The article pretty much said that unless your camera is around the 70's area, don't bother using a normal polarizer and that a circular would be the way to go due to a normal one messing with your metering. Any truth to this, have a purchased something COMPLETELY useless for the camera or is there still just as much use if not the exact same with the two i've bought?
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 11:31 am

It's easy to test.

Put the polarizer on your lens. Try to autofocus. If you can't lock on, you have a linear polarizer. If everything works, it's circular. It's worth testing this in both indoor and outdoor conditions just to be sure - I've only ever used C-PLs.

Since polarizers take quite a bit of fiddling to reach their maximum effectiveness anyway, the loss of AF is not a killer. If it's going to take you 3 minutes (okay, maybe 1) to fiddle with the orientation until you're happy with the result, you can spare the extra 15-20s to focus. You won't be using these to take action shots at a motor race.

PS It's also worth noting that I've never been able to get effects as dramatic as the example pictures on the wiki page. Most of the time, I can barely filter out reflections from glass panes -_-.
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 11:43 am

I think this might be some hint to what I got...... I just slapped it onto my 50/1.7 and as I turned the ring on the polarizer I noticed bright light highlights on the glass panes appearing and dissapearing depending on which way I turned it. Now I'm not quite sure the meaning on a Circular vs a Linear, but it sounds like the circular is adjustable and a linear in a stationary filter much like a typical UV filter, or am I completely off base?
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 12:11 pm

No, this is exactly how a polarizer is supposed to work. The only difference between a C-PL and a regular PL is that a C-PL has a half wave rectifier that changes the orientation of the light after the first pass so that it stays compatible with AF and metering systems.
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 1:05 pm

Now I'm not quite sure the meaning on a Circular vs a Linear, but it sounds like the circular is adjustable and a linear in a stationary filter much like a typical UV filter, or am I completely off base?
You're completely off base ;)
All polarizers have a rotating part and a fixed part, and both linear and circular will attenuate reflections in certain orientations as you describe; the difference between them is whether they fool the systems in the camera, not anything you can see with your eye.

I love polarizers in certain situations because they can do fairly dramatic things that are difficult or impossible to achieve in post-processing, but those are only very specific circumstances and unless you go looking for them a polarizer doesn't do much for you except making things a little darker or taking up space in your camera bag. My two favorite experiences with polarizers:
- shooting Greek and Roman ruins in the eastern Mediterranean: when I found the right relationship between myself, the sun, and the subject I could get brilliant white limestone in front of amazing blue-black skies (you can get this kind of drama with cumulus cloudscapes also)
- shooting tidepools on the northern BC coast: turning the polarizer would make the surface of the pool go from an opaque sheet of glare to transparent, almost like having X-Ray vision, and the purple and amber starfish would suddenly pop out against the kelpy backdrop

Be especially careful with cleaning polarizers, and check for scratches if you're buying used.
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 2:28 pm

Wikipedia does a nice job explaining it http://en.wikipedia.org/wiki/Circular_polarizer
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 4:52 pm

Thanks for the info guys :).

I cleaned it off with the lens papers/liquid, no scratches what so ever (Im nit picky). Like I said the Ambico one looks almost like its never been used. Its in a hard case with a almost seat Cushion foam in there as protection. I wasn't around when this company existed so I don't know the reasoning behind it, but they are impossible to find information on, looks like they went out of business. The sad part about it is that whenever I've gone through a bunch of filters, the only ones that felt truly solid and quality were these Ambico ones... just me? Maybe they are built sturdy but don't perform as well?

Either way, I was thinking of using this filter for when the Salmon run comes into town, being able to get shots of them through the river without any glare. I've seen pictures taken before where the glare hides the majority of them, pretty much ruining the shots.

Well I tried Auto-focusing and it seemed to be fine, i haven't been able to extensively test whether or not its focusing incorrectly, that doesnt mean its not going to throw the metering off though. What would be a full proof way to test it out. I'd imagine that the packaging would say SOMETHING regarding whether or not it is a C-PL or something, or when they were first getting going with C-PLs did this sort of info not get printed on packaging?
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Re: Polarizing Filters

Postposted on Thu Apr 01, 2010 7:59 pm

Most filters built in the 70s and later would be C-PL. It's the linear polarizers that are rare now. Sounds like you have a C-PL.
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Re: Polarizing Filters

Postposted on Fri Apr 02, 2010 1:25 am

Voldenuit wrote:Most filters built in the 70s and later would be C-PL. It's the linear polarizers that are rare now. Sounds like you have a C-PL.

Mmm, not necessarily. I can pick up a couple linears off Amazon right now, and they're about 1/2 to 1/3 the cost of a circular. If somebody didn't know the difference and went price shopping, they'd grab a linear by mistake.
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Re: Polarizing Filters

Postposted on Fri Apr 02, 2010 2:07 am

ludi wrote:
Voldenuit wrote:Most filters built in the 70s and later would be C-PL. It's the linear polarizers that are rare now. Sounds like you have a C-PL.

Mmm, not necessarily. I can pick up a couple linears off Amazon right now, and they're about 1/2 to 1/3 the cost of a circular. If somebody didn't know the difference and went price shopping, they'd grab a linear by mistake.


Interesting. I wonder what they'd be used for? Panfocal lenses? MF CCTV lenses?

I always just assumed they'd be more expensive these days because the main user group (in my mind) would be rangefinder users, and they're used to getting ripped off on everything.
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