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Comment by ivank | Hacker News Reader

Their FAQ says "Do 2D Glasses work at IMAX theaters? Alas, no. IMAX uses a different technology than normal movie theaters so 2D-Glasses will not work at an IMAX theater."

Anyone know how IMAX is different?

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http://en.wikipedia.org/wiki/IMAX#IMAX_3D Wikipedia suggests that IMAX 3D uses either linear polarization or LCD shutter glasses. Obviously 2-D shutter glasses wouldn't be very practical, but the polarization glasses (which I think is the standard?) should be just as feasible as the circularly polarized glasses used by RealD.

Come to think of it, normal polarized sunglasses should work as linear polarization filters assuming they line up the right way.

They do, though all I've tried have been at the wrong angle, and you just look weird holding your head at 45 degrees for 2 hours.

Every pair of polarised glasses I've tried has been polarised at a 45 degree angle; this helps with more consistent glare reduction and also means that LCD screens don't appear completely black half the time.

I've actually marked the edge of the circular polariser filter I have for my camera so I can tilt my head (wearing polarised glasses) and then quickly move the filter to match.

I thought the the point of having polarized sunglasses was that they should be polarized vertically in order to block glare (which tends to be polarized horizontally; see http://en.wikipedia.org/wiki/Brewsters_angle). Mine are, anwyay. Usually it is the LCD screens that are polarized at a 45 degree angle - for compatibility with sunglasses.

I had Lens Crafters make me a custom pair of polarized sunglasses with the polarization at 45 degrees to match up with my laptop's polarizer. Used with the laptop, they dim everything I see BUT the laptops screen. Not all laptops have the same 45 degree tilt, some are 180 from mine.

That's pretty clever. Do they enable you to use your laptop outdoors in the sun?

You would look even weirder holding one eye level, and rotating the other 90 degrees.

More than a decade ago I was an IMAX projectionist and I believe that linearly polarized glasses would work. Unfortunately these are circularly polarized.

In this Ohio theater they used a belt and suspenders approach where both polarization and timing were used to create the 3D effect. Left and right eye frames were projected through polarized filters and the projector itself was constructed so that one of the shutters would always be closed while the other was being displayed. The headsets handed out to the audience were active; they had LCD lenses and an IR receiver which would align the timing to the projector's.

This was purportedly done to increase decrease the "crosstalk" between the two eye views and worked quite well.

* Edited to reflect Cushman's observation on circular vs linear polarization.

IMAX 3D uses linear polarized light, whereas RealD uses circularly polarized light.

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