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PostPosted: Sun May 09, 2010 5:28 pm 
I'm just getting into using filters.

I bought a sunpak circular polarizer, and it definitely has an effect, but not close to the striking examples I've seen on the web.

I'm wondering whether different manufacturers' filters have a more striking polarization effect, or whether they're all more or less the same except for maybe having a different overall light attenuation or other factors?

If there is a different level of polarization effect, is there some spec for it?

What I'm trying to get at is whether it's worth spending some money for another filter - whether there is a 'stronger' polarizer ( kind of like ND filters have different 'strengths') ?

Is there a difference in strength between linear and circular polarizers ( I know about the AF issue with linear vs circular, but I'm shooting a point-and-shoot, not DSLR, so not a problem at this point)?


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PostPosted: Tue Aug 23, 2011 1:27 am 
:Bump:

At 18mm i'm gettin like 1/2 or less of a bluer sky with a cheapo Zeikos CPL filter. Seems like it takes about 40 to 50mm on the 18-70 lens before the sky finally turns a more even shade of blue over the entire DX frame.

Does a more expensive filter, or an "extra dark" create more shade over a wider angle?


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PostPosted: Tue Aug 23, 2011 4:13 am 
I've personally never seen a "strength designation" of the polarization.

But there are 2 types of polarizing filters: circular and linear.

The circular ones will vary in strength-of-effect depending on the angle of the filter. They have a front ring that rotates and you can very visibly see the the difference in levels when rotating them.

The "banding" effect of circular polarizers on wide-angle lenses is unavoidable - it's an effect of angle-of-light. Well, by unavoidable I mean at certain angles the bands will be there - however if you change your overall angle to the sun, it may not be there - but that's basically a wholly different composition so I consider these bands "unavoidable" pragmatically speaking.

Cheers :-)


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PostPosted: Thu Aug 25, 2011 1:02 am 
Image

Ok, i got a little more than 1/2 of the sky darkened with an inexpensive Zeiko CPL filter at 18mm DX. The sun is about 110º to 120º left

Now i'm wondering, if i spend more money (or perhaps a different brand) will i get a more even blue, with wide angle coverage


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PostPosted: Thu Aug 25, 2011 6:40 am 
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Circular Polarizers do vary in strength, but only in terms of how much light they block as far as I'm aware.

Obviously as you turn the circular polarizer, the effect will strengthen and if you watch your shutter speed in Aperture Priority you'll notice that the speed will slow. This can vary between brands, as well as the effect with the filter attached but set at its weakest point.

I've roughly measured the effect of my B+W, purely so I know if I'm using it in conjunction with Neutral Density filters how much I need to aim for in terms of shutter speeds for long exposures. Mine seems to be quite strong, acting as a 1 stop ND with no polarisation and a 1.7 stop ND with polarisation.

Presumably if you opt for a thin C-PL for use with wider angled lenses the ND effect will be less, but I've not tried one.


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PostPosted: Thu Aug 25, 2011 10:29 am 
Alright, thanks you all.

Oh, can an even polarizing effect be achieved by using a top dollar Adobe program - and no Lens filters at all


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PostPosted: Tue Feb 14, 2012 5:02 pm 
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A polarizer only has effect on sky color at 90° angles from the sun, or basically in N & S directions. Wide angle lenses 28mm or less, have a 70° angle or greater, thus you will have at least 20° each side of center not effected. This is true of any filter, at any price.

Polarizer's can reduce reflections from non-metallic objects in any direction, but have the most effect at 30° angles or shallower from the object. You cannot use a “Linear Polarizer” on a digital camera, it will affect both your auto focus, and TTL metering. :)

No photo editor even Adobe, can successfully imitate the true effects of a polarizing filter. :(

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PostPosted: Tue Feb 14, 2012 6:13 pm 
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Quote:
Polarizer's can reduce reflections from non-metallic objects in any direction, but have the most effect at 30° angles or shallower from the object. You cannot use a “Linear Polarizer” on a digital camera, it will affect both your auto focus, and TTL metering.


I beg to differ with this part, I have a Canon L PL-L polarising filter, and both metering and autofocus still work fine on my D2H. Could be that it's actually secretly a circular filter though, I have no way to know for sure.

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PostPosted: Tue Feb 14, 2012 6:31 pm 
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Differing noted:

I have seen some statements that certain cameras will work with L-polarizers, but its not common across the board. Its best to be safe, and make certain you have a circular polarizer. :)

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