Dual Projector Circular Polarizing Filter

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AdmiralMH
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Dual Projector Circular Polarizing Filter

Post by AdmiralMH »

Hi, I'm trying to get a 3D dual projector rig set up and I have about everything figured out but the filters. Do you guys know which circular polarizing filter would be the best choice for me. My projector will be a Canon REALiS SX80 Mark II D and it gives about 3000 lumens max. I'm trying to use a short throw distance so I'll need either a heat resistant filter to place it close up or large filter for further away. I've checked out some filters on the net already but the best 3D projector dedicated filter I've seen so far is the one on berezin.com. And even the plastic circular filters are expensive!

Are there any cheap, quality alternatives? Or can I use a camera polarizing filter?

Thanks,

AdmiralMH

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Likay
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Re: Dual Projector Circular Polarizing Filter

Post by Likay »

1st: You have to take my words for it but get linear filters instead! They ghosts half as much as circular (in other words ghosting gets close to nonexistant) and you will not gain anything being able to tilt your head anyway. Stereoimages are rendered horisontally and turning the head cause the 3d-image to be distorted/lost even when using circular polarization. You can test this with anaglyph glasses and shuttertechnology which is independant of rotating.
Even more: When watching stereomovies or gaming in stereo the brain tries to maintain the best stereopsys by adjusting your head until it's aligned the same as the rendering of the media. This causes the viewer having a perfectly horisontal aligned head anyway. Circular filters ghosts more than linear because of rules of nature (easy explained... lol) because of the way they works. They are a 2-layer construction and the extra layer (retarder) causes both colordistortion as well as more ghosting. Colordistortion is very light and will not have a visual impact on the final image though. Regradless: The resulting image from linear polarization is more than twice as better than using circular.

3000 lumen is quite bright for projectors and you're right that filters easily fries at those levels. I've tried myself with plastic filters from polarization.com and they lasts 50 hours+ (i removed them and uses the spars (lcd-projectors only) because of better image but those plastic filters would have lasted a lot more) with my 2500 lumen projectors. The "shining area" on the plastic filters was approximately 40x50mm and the distance to the lenses 7 centimetres. According to another user here this seems to be the painlevel for what plastic filters are able to handle. So with 3000 lumens you should have a "shining area" of about 60x50mm's. Adjust the distance between the lense and filter until you have this area (and a little more would probably not hurt).
Glasses filters are generally more resistant to radiation and should handle the 3000 lumens without problems. Be sure to check specifications on the filters first!
Last edited by Likay on Sun Feb 14, 2010 7:59 am, edited 2 times in total.
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AdmiralMH
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Re: Dual Projector Circular Polarizing Filter

Post by AdmiralMH »

Thanks, for all the info. I tried out the anaglyph version for head tilting and yeah you're right. I'll see what I can do with the linear and circular filters.

AdmiralMH

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Re: Dual Projector Circular Polarizing Filter

Post by relaxman »

i also recommend linear.
we orderer circular and also linear from polarization.com,
and the circular ghost badly when a high contrast scene present.
Linear version has almost 0 ghosting!

Cleeve
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Re: Dual Projector Circular Polarizing Filter

Post by Cleeve »

Can you point me out to which product exactly I should be purchasing on Polarization.com?

http://polarization.com/polarshop/" onclick="window.open(this.href);return false;

Polarizer film, polarizer sheets,...? I'm just not sure what I need.

Thanks!

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Likay
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Re: Dual Projector Circular Polarizing Filter

Post by Likay »

Thick, good filter, also the most expensiest. I've tried with this with good results once: http://www.polarization.com/polarshop/p ... f78c2efd68" onclick="window.open(this.href);return false;

This should also work splendid: http://www.polarization.com/polarshop/p ... f78c2efd68" onclick="window.open(this.href);return false;

and also this: http://www.polarization.com/polarshop/p ... f78c2efd68" onclick="window.open(this.href);return false;

You need to be watchful though: it seems like polarization.com have the same articlenumber for sheets with adhesive as well as without. You need filters WITHOUT adhesive layer so you need to notify them about this.
Mb: Asus P5W DH Deluxe
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3D:100" passive projector polarized setup + 22" IZ3D
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Cleeve
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Re: Dual Projector Circular Polarizing Filter

Post by Cleeve »

Thanks Likay!

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Re: Dual Projector Circular Polarizing Filter

Post by AntiCatalyst »

epic necropost(not good for a first post lol :D), and OP has probably gotten his polarizers already but this one is for everyone else:

the plastic cpl's from polarization.com seem to be absolute rubbish! i compared them side by side to the lenses in my look3d disposables(!) and the extinction in them is at least two times better than the polarization.com filters! seems to be more sensitive to rotation though(i thought cpls didn't care how you move your head)

it must be the wave retarder that's much much worse, because they do extinct fine when flipped over to linear mode.

now if i could just get ahold of some of them look3d polarizer sheets ;)
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Likay
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Re: Dual Projector Circular Polarizing Filter

Post by Likay »

Are you sure that you aren't using the filters "wrong way"? Circular filters only works properly in one direction while linear works twoways (circular also works like linear filters when used the wrong direction).
I got linear as well as circular sheets from polarization.com and linear have twice the extinctionrate as circular. I've compared with two different models of real-d glasses and a pair of circular polarized cameralenses. There was no noticeable difference between the different real-d's and polarization.com's circular filters but the camerafilters caused a tiny bit more ghosting then the others. All circular filters ghosts about twice as much as linear though. The usual phenomenas i got with circular compared to linear is that circular filters gives a "washed out" image compared to linear. Circular filters aren't sensitive for rotation if they're pure circular filters but some discoloring/ghosting can occur during rotation anyway.
Mb: Asus P5W DH Deluxe
Cpu: C2D E6600
Gb: Nvidia 7900GT + 8800GTX
3D:100" passive projector polarized setup + 22" IZ3D
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AntiCatalyst
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Re: Dual Projector Circular Polarizing Filter

Post by AntiCatalyst »

yes, the filters are the right way, i'm not that stupid ;)

i do however have a theory on the color tint..
quarter wave plates are really only good for a single wavelength(usually green). This means that no matter what, all wavelengths other than green WILL end up
more or less ellipctical instead of the completely circular waves that we want.

now, when we rotate the cpl, we clearly see that there are two distinct ways of holding the filter.. the "wrong" way with magenta color tint, and the "right" way when rotated 90 degrees.

this happens because we are essentially aligning the quarter wave plate either to enhance the elliptical waves created by the first filter, or to undo them.


when holding it the wrong way, only green light gets properly retarded back into linearly polarized light(since it's perfectly circular) and absorbed by the polarizer. Other wavelengths are now made even more elliptical as they pass through the wave plate. this means they will pass through the polarizer quite easily. This is the reason for the magenta tint - Green gets cut, and red and blue pass right through the polarizer.

in the other case(the right way), a tiny bit of light will pass through the polarizer due to imperfect wave plates, but the end result is still a very usable image


now this is just what my common sense thinks is going on, I'm not a physicist or anything.

i did however get an MVG in fysik B :D
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