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How to use a Circular polariser
- Thread starter ziggy©
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- Richard
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Well, the bit about a circular polariser being a linear poliser with a quarter wave plate on the back is true enough, so they don't upset AF and AE systems, but the rest is not.
In terms of polarising effect, linear and cirular work exactly the same at all times, there's no such thing as left and right handed polarisers and the only thing that polarisers don't work with is reflections off metal so the coin thing will not show any difference.
If you want to know if you have a circular or linear polariser, if it doesn't say so on the rim, then if you look through a circular polariser from the normal lens side it will polarise, turn it round and look through the other side and it will not - the quarter wave foil must be always be on the lens/camera side.
Another tip which I learnt the expensive way at the weekend :bonk:- when rotating the polariser, always rotate it the same direction as fitting the filter - that way, if it's not on tight enough, and you are over the top of water when using it............:bang:
I won't forget that once I've bought a replacement
Very good point. A while ago, I did the same thing when out in the country and only realised a little later that it had fallen off! Took 20 minutes of retracing steps to find it. Luckily I found it and it had landed on some soft grass and was undamaged.
Easy thing to do.
Good tip.
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I've just finished reviewing 12 different polarisers for a magazine test, including linear, and I beg to differ. Not surprising really, as a circular polariser is just a linear polariser with a 'circularising' quarter wave plate on the rear. All the polarising is done before it gets to that bit. It cannot 'undo' it.
There are differences between different polarising filters, but not in terms of polarising ability. That was one of the key objectives of the test. Differences in density, colour, flare resistance, coating, mount, but not polarising ability. Decent ones don't impact sharpness either, but cheap ones can.
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Dino f
Wiiiiilmmmaaaaaaaa
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- Dean Feltimo
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HoppyUK said:
Circular polariser is available in left and right handed versions. I don't mean you turn the ring in a different direction, it's just the way they filter light rays.
Also, if you hold a coin against a circular polariser it will turn black, not because it's polarising light, but is cross polarising itself. It's a std test in the industry to determine which side the retarder is on.
Dean.
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Differ all you wish. You will not prevail over my first hand evidence.