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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Weird motion artifacts during DLP presentation (Page 1)

 
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Author Topic: Weird motion artifacts during DLP presentation
Aaron Haney
Master Film Handler

Posts: 265
From: Cupertino, CA, USA
Registered: Jan 2001


 - posted 05-22-2006 10:25 PM      Profile for Aaron Haney   Email Aaron Haney   Send New Private Message       Edit/Delete Post 
This weekend I went to see "Over the Hedge" at the Century 22 in San Jose (on Winchester Blvd). The movie was presented via a 2K DLP projector with the Dolby Digital Cinema logo shown before the feature. Aside from the usual DLP limitations (mediocre resolution and poor black level), I was surprised to notice a strange motion articfact visible during the show.

Whenever there was an image onscreen with slow, even movement, such as slow camera pan, I could see various details in the image blur momentarily, over and over, about once every second or so. It looked like a video compression problem, although not the type I am normally used to.

It was most noticiable during the end credits, which are so blurry as to be nearly unreadable, but I also saw it at various other times during the movie, including the trailers at the beginning of the show.

Has anyone else been to this theater and noticed the problem? I've been to a lot of theatrical DLP presentations, but this is the first one I've seen with this particular defect.

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Tommie Evans
Expert Film Handler

Posts: 116
From: Birmingham, West Midlands, UK
Registered: Sep 2004


 - posted 05-23-2006 01:03 PM      Profile for Tommie Evans   Email Tommie Evans   Send New Private Message       Edit/Delete Post 
Hi Aaron

I take it the DLP presentation you saw in 2k had the 3 mirror system and not a single mirror and colour wheel? Usually with a colour wheel if you move your head/vision from side-to-side you can see the colours 'break-down' on the contours of shapes in the image. Possibly the colour wheel had been knocked or damaged?

Another occurance, especially with computer generated images is that the over-sampling of pixels or aliasing might be ropey in some details i.e. fur and blades of grass as an example, but usually this is seen as a shimmering effect within the pixels?

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Darryl Spicer
Film God

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From: Lexington, KY, USA
Registered: Dec 2000


 - posted 05-23-2006 04:23 PM      Profile for Darryl Spicer     Send New Private Message       Edit/Delete Post 
I thought they would all be the three mirror dlp chips in use on professional equipment.

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Aaron Haney
Master Film Handler

Posts: 265
From: Cupertino, CA, USA
Registered: Jan 2001


 - posted 05-23-2006 04:41 PM      Profile for Aaron Haney   Email Aaron Haney   Send New Private Message       Edit/Delete Post 
I'm under the impression this is a three chip installation. I'm familiar with what colorwheel effects look like, and this looked very different. It also did not look like any aliasing effect I'm familiar with. It's very hard to describe. Imagine an object is moving across the screen steadily, and once every second or so, it blurs or smears along its direction of motion, just for a frame or two. I wish I could describe it more clearly, but it's one of those things you just have to see for yourself.

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Alan Gouger
Master Film Handler

Posts: 474
From: Bradenton, FL, USA
Registered: Jul 2000


 - posted 05-23-2006 05:24 PM      Profile for Alan Gouger   Author's Homepage   Email Alan Gouger   Send New Private Message       Edit/Delete Post 
Did you see this during the movie as well. If it was limited to just the intro it is possible what you saw was caused from the intro material originating from 30 FPS video.

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Aaron Haney
Master Film Handler

Posts: 265
From: Cupertino, CA, USA
Registered: Jan 2001


 - posted 05-23-2006 09:55 PM      Profile for Aaron Haney   Email Aaron Haney   Send New Private Message       Edit/Delete Post 
It was during the entire feature.

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Frank Angel
Film God

Posts: 5196
From: Brooklyn NY USA
Registered: Dec 1999


 - posted 05-24-2006 04:50 AM      Profile for Frank Angel   Author's Homepage   Email Frank Angel   Send New Private Message       Edit/Delete Post 
So what are you saying....there can actually be flaws in digital? GHASP! But....but, my dreams are shattered....they told us that only FILM had flaws...especially after a few showings; you know, it gets scratched and dirty and looses all its color. On the other hand, digital is the same the billionth effin time it is viewed as it is the first time.....that is, with its low contrast, poor blacks, soft images and now we discover, glory be, motion artifacts that cause in-and-out-of- focus it the camera pans. Oh my, who woulda thunk it?! It's great for STILL pictures; with movies.....not so good.

OK, enuf sarcasm....but this just goes to show, what every techie knows, that NO technology is perfect. I wish the digevangelists would just admit that and stop bashing film that has served us for a century.

It's really a matter of what exactly the imperfections are. Personally I think I am a lot more comfortable with some flects of random dirt rather than a continuous focus flutter on all camera movement once every second. And I assume this projector was relatively new....like it's probably been in service all of a year or two and played, what, a dozen or so features if that?

Yet, their's my "old technology" as they are now refering to 35mm film, my trusty Simplex XL that hasn't broken down in more years than most of the TI tech guys have been alive. Let's see the longevity track record of the current 2K digital "roll out." Bet the exhibitors who are shelling out $100,000 per screen to get on this 2K "bandwagon" (1200 screens out of 36,000...some bandwagon) are hoping it their longevity will be a tad longer than the life of those 1.3K digital projectors of the once lauded 1.3K rollout.

Ah, hope springs eternal. Sorry, guys I think the sarcastic button must be stuck.

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Louis Bornwasser
Film God

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From: prospect ky usa
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 - posted 05-24-2006 09:10 AM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Remember, PR being what it is, there is no ad revenue for old stuff, so 'zines will "push" that which pays the ads.

I still have never seen or heard of a completely fair "shootout". I find this to be the height of disingenuousness. Should not the wattage be matched? Should not we look at "mixed media?" (Not cartoons.) Louis

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Paul Konen
Jedi Master Film Handler

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From: Frisco, TX. (North of Dallas)
Registered: Jun 99


 - posted 05-24-2006 10:09 AM      Profile for Paul Konen   Email Paul Konen   Send New Private Message       Edit/Delete Post 
All professional DLP systems are 3 chip systems. No color wheel.

I've seen artifacts when watching Cable TV, but have yet to see it with DLP. I've been looking because of what you guys have said too.

I don't see how there could be artifacts when each frame is scanned , encoded, and projected individually. It isn't done like early internet video where you would get an initial frame and then as it played, the resolution would improve.

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Jack Ondracek
Film God

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From: Port Orchard, WA, USA
Registered: Oct 2002


 - posted 05-24-2006 11:08 AM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
Could this be a server problem?

During the recent demo at the Transit Drive-In, I was able to watch the server "at work" (though the problems described here weren't observed at the demo). Actually, if it weren't for a little blinking light, one wouldn't have necessarily noticed it. Assuming the flashing had something to do with periodic data transfer from the hard drive to a buffer, I wonder if that might have been related to what Aaron saw.

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Mattias Ohlson
Expert Film Handler

Posts: 180
From: Falun, Sweden
Registered: Mar 2003


 - posted 05-24-2006 11:19 AM      Profile for Mattias Ohlson   Email Mattias Ohlson   Send New Private Message       Edit/Delete Post 
I think that the artifact described is called error diffusion or motion contouring. From what I understand dlp cheats in using some spatial real estate to render gradients. With moving objects there can be problems. The thing is that this artifact goes unnoticeable by many people.
I am surprised the artifact is described as so noticeable.
Thus 4k sxrd should be the choice for digital cinema. [Smile]

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Frank Angel
Film God

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From: Brooklyn NY USA
Registered: Dec 1999


 - posted 05-24-2006 12:52 PM      Profile for Frank Angel   Author's Homepage   Email Frank Angel   Send New Private Message       Edit/Delete Post 
quote: Paul Konen
I don't see how there could be artifacts when each frame is scanned , encoded, and projected individually. It isn't done like early internet video where you would get an initial frame and then as it played, the resolution would improve.
Well that's the point, isn't it. We don't see how this can happen because it doesn't with a perfect system, but obviously things can and do go wrong. There shouldn't be scratches on film, but when things go wrong, there they are.

It would be much better if we KNEW about potentially presentation ruining anomolies of the digital system. There is no such thing as perfect technology, each has imperfections that have to be learned and dealt with. Sure these anomolies aren't supposed to happen in a perfectly tweaked system but obviously they do can be addressed and probably corrected because they are not inherent in the technology.

By the same token, that can also be said of film. All the film bashing that goes on is about stuff that is easily dealt with if film is done right. So the bashing is not valid. Likewise to bash digital because of these peculiar anomolies is equally invalid. How about let's recognize and evalutate the each technology with full knowledge of what problems may present themselves down the line.

It sure would be nice to know about all the potential tech problems that an exhibitor may face BEFORE he plunks down very big bucks to convert -- it should ALL be on the table if exhibition is has any chance of making an informed decision. That objectivity seems to be out the window when it comes to the digital conversion (tell me again how those pesky little nano-mirrors age....what?, no one has come forward with a study about that so far?.....well you know they are going to, and I bet it isn't gonna be very pretty....or cheap to fix).

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John Pytlak
Film God

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From: Rochester, NY 14650-1922
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 - posted 05-24-2006 02:27 PM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
Texas Instruments published quite a few "white papers" about DLP technology, including reliability studies:

TI DLP "White Papers"

quote:
Development of the Digital Micromirror Device (DMD) Microsystem

9/7/2005
Author(s): Michael R. Douglass

Abstract: The Digital Micromirror Device (DMD) developed by Texas Instruments has made tremendous progress in both performance and reliability since it was first invented in 1987. From the first working concept of a bistable mirror, the DMD is now providing high-brightness, high-contrast, and high-reliability in over 5,000,000 projectors using Digital Light Processing™ technology. In recent years, the DMD has achieved the status of being a commercially successful MEMS device. The knowledge we gained through our characterization and testing helped us achieve this success. The performance of our production DMD has achieved, and in some cases exceeded, our reliability goals. For every new DMD as well as for each major design change, Texas Instruments performs a detailed failure modes and effects analysis (FMEA). This process assures the standards achieved for reliability and performance are maintained on all subsequent designs. This paper discusses some of the metrology developed for the DMD, accelerated stress testing techniques, environmental testing, unique DMD life tests, test equipment development, packaging, modeling and failure analysis. The use of characterization and testing and how they were essential to achieve our reliability goals will be discussed. Keywords: DLP™, DMD, MEMS, testing, characterization, reliability, picture reliability...

Development of DLP


quote:

4/10/2003
Author(s): A.B. Sontheimer and D.J. Mehrl

Abstract: This paper will show how different operating conditions improve hinge memory lifetime of the Digital Micromirror Device (DMD). The correlation of parametric measurements to physical properties will also be developed. Specific operating conditions explored include the effects of (1) on/off duty cycle, (2) relaxation during nonoperation and (3) reversibility on hinge memory lifetime performance.

DLP Hinge Memory Test


quote:
Lifetime Estimates and Unique Failure Mechanisms of the Digital Micromirror Device™

2/4/1998
Author(s): M.R. Douglass

Abstract: This paper discusses Digital Micromirror Device (DMD) reliability development activities; failure modes investigated (e.g., hinge fatigue, hinge memory, stuck mirrors, and environmental robustness); various acceleration techniques (e.g., temperature and duty cycle); corrective actions implemented; and the resulting evidence that the DMD is exceeding original reliability goals.

DLP Failure Modes


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Aaron Haney
Master Film Handler

Posts: 265
From: Cupertino, CA, USA
Registered: Jan 2001


 - posted 05-24-2006 05:15 PM      Profile for Aaron Haney   Email Aaron Haney   Send New Private Message       Edit/Delete Post 
I should point out that I've seen two other features in DLP at this theater since they installed the Dolby 2K system, namely "Sin City" and "Harry Potter and the Goblet of Fire", and neither of them exhibited the problem.

Also, I have to say that speculation is probably pointless. Without more information, there is no way of knowing where the problem originated. It could be the result of something going wrong anywhere along the chain from the final render to the compression stage to the physical projector. I sent Century a feedback note on their website. Hopefully someone with some technical know-how will go by and take a look.

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Bill Enos
Film God

Posts: 2081
From: Richmond, Virginia, USA
Registered: Apr 2000


 - posted 05-24-2006 05:46 PM      Profile for Bill Enos   Email Bill Enos   Send New Private Message       Edit/Delete Post 
Re DLP white papers----An engineering smoke screen-no useful information contained.

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