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Author Topic: Digital preshow projector and 3D glasses Thomas Pitt Master Film Handler Posts: 266 From: Leeds, West Yorkshire, UK Registered: May 2007 posted 09-13-2007 03:34 PM                     This has been bugging me for a while now, and since I visited the Bradford IMAX today I thought I might ask here. Like many venues, the Bradford IMAX uses a standard LCD data projector (connected to a laptop) to run pre-show slides on a looping Powerpoint presentation. If you are in the auditorium, and put on your 3D glasses while the pre-show is running, an odd effect occurs. The left eye sees just the Red and Blue channels of the RGB signal, while the right eye sees only the Green channel. I've never seen this effect before on LCD screens, or on data projectors when using polarized sunglasses. I assume it's got something to do with the IMAX screen being silver to maintain polarization, and the glasses having two polarizing filters at 90 degrees to each other. But I still don't know exactly why it happens! Has anyone with digital projectors and silver screens seen this effect, and know why it happens? Also, just noticed today they had what appeared to be newly made 3D glasses. These do not show the color-change effect when you have your eyes level - but tilt your head 45 degrees, and you see the colors separate again.  |  IP: Logged Dick Vaughan Phenomenal Film Handler Posts: 1032 From: Bradford, West Yorkshire, UK Registered: Jul 2000 posted 09-14-2007 03:29 AM                        Not really a large format question so should probably move to another forum but here goes quote: Thomas Pitt Also, just noticed today they had what appeared to be newly made 3D glasses. These do not show the color-change effect when you have your eyes level - but tilt your head 45 degrees, and you see the colors separate again. The orange framed glasses we previously used had 0/90 polarisers that is the axes of polarisation were vertical and horizontal. The new powder blue are aligned at 45 degrees to the horizontal like so /\. The projector isn't digital ie using a DLP chip or chips just a plain old Sanyo PLC XP46. It uses 3 TFT LCD panels presumably 2 are aligned in one direction and the 3rd is at 90 degrees to the other 2. If you try looking at a laptop or other lcd computer screen through linear polarised glasse you will get a similar black out effect.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 09-14-2007 06:53 AM                     Dick, What was the reason for the change in polarisation angles? I believe that 45 degree angles in traditional 3-D with disposable cardboard glasses was to ensure that the system would work correctly whichever way the user put the glasses on.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 09-25-2007 06:52 AM                        When I saw THE LAST BUFFALO at the Vancouver IMAX (at the time --early 1990s -- I think it was the only IMAX in Vancouver -- on the water in some sort of museum), the floor manager told me that the glasses they were using were the new "circular polarization" type which had the advantage of not being affected by how level the patrons kept their heads. I never heard of this and pretty much never really persued what it actually means. "Disney 3D" MEET THE ROBINSONS also claimed that the RealD system used circular polarization. Exactly what is this and is it different than 45/45? BTW, THE LAST BUFFALO is a truely fantastic piece of filmmaking irrespective of the 3D element (although that element is truly awesome and some of the best dimentional cinematography I have ever seen) and in my opinion was Academy Award material, hands down. From my recollection, there was no narration at all and the entire concept unfolded only thru the visual content, juxtaposing nature and art. Simply beautiful. I would give anything to see this again in IMAX 3D. Anyone know if IMAX films have ever nominated or won an Academy Award, as this surely was worthy? I also thought NORTH OF SUPERIOR was a great film (and my first IMAX experience); I was so impressed at the time with the filmmaking, again irrespective of the IMAX process, that I contacted the company to see if I could book it as a special event in my theatre, in 35mm if they had struck a 35mm work print of some sort. I was even willing to install 70mm at the time if they could get a 70mm print (normal horizontal system, of course). Naturally they said emphatically NO because the IMAX titles would ONLY be available on IMAX screens, EVER. Little did I know that all I had to do was wait them out a few years to see the IMAX titles made available on Laserdiscs and DVDs where the IMAX experience could be experienced on a 19in TV sets. Even IMAX is a whore.  |  IP: Logged Dick Vaughan Phenomenal Film Handler Posts: 1032 From: Bradford, West Yorkshire, UK Registered: Jul 2000 posted 09-25-2007 09:00 AM                        Frank Better pack a bag and get out here to Vancouver as Last Buffalo is here  |  IP: Logged Jeffry L. Johnson Jedi Master Film Handler Posts: 809 From: Cleveland, Ohio, USA Registered: Apr 2000 posted 09-25-2007 02:21 PM                        As far as I know, The Old Man and the Sea (1999) is the only Academy Award winning IMAX format film. Old Man and the Sea IMDb Vancouver has both an IMAX Dome screen and the first IMAX 3-D screen. These were built for EXPO 86. TELUS World of Science Omnimax® Theatre IMAX® Theatre at Canada Place  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 07-17-2011 03:26 PM                 It has been 1391 days since the last post.  |  IP: Logged Sean Weitzel Jedi Master Film Handler Posts: 619 From: Vacaville, CA (1790 miles west of Rockwall) Registered: Dec 1999 posted 07-17-2011 03:26 PM                     Hopefully on topic: I recently attended a screening of a 15/70mm 3d feature at the Esquire Imax in Sacramento Ca and found them to be using glasses I have not encountered anywhere else. They appeared to be polarized, but had different color tint on each eye kind of like old anaglyph red/blue (I think this was blue/yellow). Is this some kind of new technique? I will have to say the cross talk between each eye was much better than the other nearby 15/70mm imax theater I frequent has uses conventional polarized glasses. When I took the glasses off during the end credits it did appear that the two eyes might have been color timed a bit different.  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 07-17-2011 06:58 PM                     Colorcode is the blue/yellow process. Not sure why a corporate Imax theatre would be using a non-Imax process. What movie was it?  |  IP: Logged Sean Weitzel Jedi Master Film Handler Posts: 619 From: Vacaville, CA (1790 miles west of Rockwall) Registered: Dec 1999 posted 07-18-2011 01:53 PM                     The final Harry Potter. FWIW the glasses had the word IMAX printed on the frames.  |  IP: Logged

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