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Author Topic: 3D Ghosting Larry Zuverink Film Handler Posts: 98 From: Caledonia, MI, USA Registered: Nov 2002 posted 10-19-2007 02:46 PM                     Anyone have any idea what causes 3D ghosting. We were told that Hurley screens cause this. However we have 4 screens not doing it and one that is. Of course Christie and Real D both blame the screen. All 5 of these screens are brand new.  |  IP: Logged David Zylstra Master Film Handler Posts: 432 From: Novi, MI, USA Registered: Mar 2007 posted 10-19-2007 04:15 PM                     I know that certain 3D technologies require what they call "ghost busting" where they do something to each eye's picture to cancel out bleed through of the polarizers (this was why DCI came up with a spec for 3D to work towards single inventory and put "ghost busting" responsibility onto the hardware). One thing to check would be to make sure the copy of NBC in question is one that is meant for RealD and not Dolby or another 3D system - I wonder if somehow that screen has a non-"ghost busted" DCP . . . . . sheer speculation on my part.  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 10-19-2007 05:51 PM                     I assume you have made sure that the Z-Screen is fully in place and completely level. How can you tell if the copy of NBC is intended for Real D? I had an issue with mine. It was somewhat noticeable with the pumpkin policy. The screen is a Harkness 240, same as we have used in the past for Meet The Robinsons, and I did not have this problem before. I wonder if it could have anything to do with the fact that in this auditorium the projector is slightly angled because it is off-center. I could not shift the lense far enough to get the image centered without vignetting, so I had to angle the projector. Could the ghosting at all be the result of the fact that the projector is not exactly perpendicular to the screen? (Wondering if that affects the polarization at all.)  |  IP: Logged David Zylstra Master Film Handler Posts: 432 From: Novi, MI, USA Registered: Mar 2007 posted 10-19-2007 08:15 PM                     If it worked for MTR then it should work for NBC . . . . . . the only thing I found that would show which system the DCP is for is "GB" on the hard drive label (I assume "GB" = "Ghost Busted"), but the wrong label could have been put on the wrong hard drive. Our original RealD for Monster House was set up with the digital projector off center due to the 35mm still being in place and we did not have any trouble like this so I don't think the angle is it. I think the only way to prove if it is content related is to play test content that is known to be truly for RealD (if you had any trailers left over from MTR that would work - but I'm sure it has all been deleted by now).  |  IP: Logged Larry Zuverink Film Handler Posts: 98 From: Caledonia, MI, USA Registered: Nov 2002 posted 10-20-2007 09:17 AM                     Hey Dave, Good to hear from you. So If I understand you corectly I should be able to bring content from a theatre that is not ghosting, that should tell me if it a ghost busting problem.  |  IP: Logged Chris Slycord Film God Posts: 2986 From: 퍼항시, 경상푹도, South Korea Registered: Mar 2007 posted 10-20-2007 09:36 AM                     If the problem is the content itself and not the projector/screen, then yeah it would stand to reason that putting in known good content would display fine. And if it still doesn't work, you know it wasn't the contents that were messed up.  |  IP: Logged Scott McGuire Film Handler Posts: 94 From: Elmira, NY/United States Registered: Oct 2007 posted 10-20-2007 11:26 AM                     Or you could take what could be that possible bad content and run it in a projector that is not ghosting. same thing either way.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 10-20-2007 12:49 PM                    When it comes to the content I would think it is from the same hard drive for all screens. In the digital world you would not need more than one hard drive. Just load the content to each server or a central server with the one drive. Try restarting the Real-D unit and run the test pattern provided for the Nightmare Before Christmas program. Check to make sure you see the left eye word with your right eye closed and vice verse. If you do not see this correctly flip the phasing switch on the back of the Real-D unit. I don't know if that will fix the ghosting problem but it's worth a shot.  |  IP: Logged David Zylstra Master Film Handler Posts: 432 From: Novi, MI, USA Registered: Mar 2007 posted 10-20-2007 02:47 PM                     Darryl - each 3D system/server combination requires special encoding - i.e. for MTR I heard there were 7 different DCP masters created due to quirks of each server manufacturer and 3D system (i.e. a copy that worked on a DoReMi/RealD would not work properly on a DoReMi/Dolby3D or Dolby/Dolby3D, etc). Larry - Yes I would verify that the content between locations work - in the interest of time (and if the trailers show the same ghosting) you can just try the trailers from the HD instead of the entire feature.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-20-2007 03:31 PM                     Is the ghosting problem an artifact generated by the single projector systems... real-D or Dolby 3-D? BTW David: Dolby has not licensed any other server manuafacturers as of yet to include their 3-D system but they anticipate doing so right after the first of the year. I have a two projector 3-D install comming up soon so it'll be very interesting to see if any ghosting problems exist. I've seen other two projector 3-D systems and there was no obvious ghosting issue. Mark  |  IP: Logged Larry Zuverink Film Handler Posts: 98 From: Caledonia, MI, USA Registered: Nov 2002 posted 10-20-2007 04:24 PM                     Sorry, It's a Christie CP2000 Projector, Doremi Server, and a Real d Z Screen system. The Christie tech says everything is set up correctly and they are blaming the Hurley screen. RealD does not recommend Hurley. Hurley however has not heard of any 3D problems with their screens. The ghosting as I called it is most noticeable on the Nightmare 3D preview when the pumpkin head comes out of the screen. It looks like a larger soft image of the pumpkin on both sides. It is eye specific. If you close your left eye only the right image and the right larger soft image (off the right side) is visible. I also removed the porthole window to make sure that it wasn't a weird reflection between the Z Screen and the port hole.  |  IP: Logged David Zylstra Master Film Handler Posts: 432 From: Novi, MI, USA Registered: Mar 2007 posted 10-20-2007 05:12 PM                     quote: Mark Gulbrandsen BTW David: Dolby has not licensed any other server manuafacturers as of yet to include their 3-D system but they anticipate doing so right after the first of the year. At ShowEast DoReMi told me that their server worked with Dolby, but I didn't pursue any further specifics on "right now" or "coming soon". . . . . The way I understand the ghosting is that it is bleed through of the polarizers - i.e. the right eye lens cannot completely block the left eye information and vice-versa so they do something to each eye's image that cancels out the "ghost" . . . . . I'm not sure which systems are subject to this effect, but if a 2 projector install uses the same type of polarizer it might be. Just a thought - I wonder if the cause could be bad glasses? taking a pair from a good location would easily prove that.  |  IP: Logged Tristan Lane Master Film Handler Posts: 444 From: Nampa, Idaho Registered: Feb 2002 posted 10-20-2007 08:11 PM                     quote: David Zylstra DoReMi told me that their server worked with Dolby Doubtful, since the color correction required by the Dolby 3D system is done within the player, not in the projector. In fact, If I understand the system correctly, you could utilize the factory color settings and still achieve proper color by correcting it with the Dolby player. Doremi may be working on adding the color correction functionality to their software but that is just speculation. The question I have is: Will the current Doremi hardware support the additional resource demands of color correcting? The reason for doing it within the player is because each eye requires a separate MCGD. In regards to ghosting: There's a number of reasons the ghosting could be happening. - Think of it like a shutter timing issue, where if the active polarizer isn't timed correctly with the frames being displayed, causing a partial bleed to the other eye. - Faulty polarizer or glasses, that aren't "filtering" each eye fully. - The screen surface may not be maintaining the polarization properly. - The controller for the z-screen isn't set up correctly - Or, you may be noticing what another forum member has described as a latency issue caused by alternating left/right frames from the single projector. Question Does the ghosting appear similar to travel ghost? (i.e.: it is only appearing on one side of a specific object or area?") Or is it appearing on either side of the image?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-20-2007 11:21 PM                     Paul Pearson told me at Shoeast that Dolby will begin licensing their 3-D stuff to other server manufacturers. Dolby has evidently realized that they alone with just a pittance of servers out there can't make a return on installing it on just their own processors. Mark  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 10-21-2007 08:19 AM                     Hi Tristan. Good to hear from you. Hope things are well. In my case, the ghosting was on both sides. It was particularly noticeable with the pumpkin. Also noticeable during the Disney 3D test frame. When I would close my right eye, I could clearly see the word LEFT, which tells me the phasing was okay, but I could also see a very faint image of the word RIGHT. And vice versa. I am going to go back and check my MTR locations, but I don't recall this happening there. Good idea to check with different pairs of glasses. If that doesn't turn out to be the problem, how can you determine if the problem is with the Z-Screen or Real D controller box?  |  IP: Logged

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