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Discussion Starter · #1 ·
CAUTION: READ THIS AT YOUR OWN RISK!!


There has been an interesting discussion on this forum about the Matrix Effect and DLPs. Would someone kindly check this out with the expensive DLPs - Sharp, Dwin, and Selecos.


Here's what to look for - during panning scenes take your eyes off the main subject area and focus closer on the edges of the screen and watch for a defocusing and breakup (blurring) of objects. This is subtle, but once you see it - well, you see it!


Here's the interesting part - Toy Story 2 - I don't see any at all!!!


The first Toy Story - all over the place??? Same story as you go from DVD to DVD. How come?


Cheers,


Grant


Hey, I didn't start the fire!
 

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I think you are referring to "videonuts" problem with XGA dlps, and apparently is the DMD itself that is at fault. apparently TI has said (paraphrasing from other threads) that the refresh rate on the XGA chip is slower than the SVGA chips, and this blurring/breakup can occur.


The Good, Bad, and Ugly scene that videonut posted is a perfect example, and looks really bad.


Also, this can be noticed on Starship Troopers in the beginning when they arrive at boot camp, and the sarge is yelling at the recruits. Alot of panning, and a lot of problems on the XGA units here.


We did testing on the Seleco 250 which exhibitied teh problem, but the 200DM does not have it. Apparently the 200 doesn't either.



Hope this is what you are referring to Grant!
 

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Does this mean that LT85 won't have the artifacts being SVGA? I'd rather sit further back and use SVGA and avoid these artifacts than being able to sit closer for XGA and get these problems. I know SVGA will be poor choice for HDTV but I don't watch HDTV. Please advise.


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Huey ;-]
 

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Discussion Starter · #4 ·
I think Robert and I are on the same wave length with respect to "Matrix". Li On do you see a Matrix effect in panning scenes - object comes apart and then back together? Look at the intro to this forum when David and Alan slide across the screen - blurs but comes together at the end.


I don't think I see dithering from 16 feet away, so for me, it's not an issue. I do see this Matrix effect.


Cheers,


Grant
 

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Discussion Starter · #5 ·
Robert, you hit the nail on the head! Great review of dithering and the Matrix!


I really believe the "Matrix" is related, at least to some degree, to the DVD itself. Please have a look for it on your D-ILA, since you are probably one of the few unlucky enough to know what the Matrix looks like - at least I am not alone in my misery.


Give this little thing the DVD transfer it deserves and hold on - this projector continues to amaze me. If NEC ever got serious about HT they could dominate the market!


Cheers,


Grant
 

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Boy, this issue is really confounding me.

I have had about 5 times in the year the following problem, which sounds like "dithering". I will turn on my Davis 650 clone (an XGA DLP) and notice after a few minutes that the colors are not right.

Faces are broken down into much fewer shades than is normal. Dark shadows are severely posterized and green in tint. It's as if the color depth has been dramatically reduced.

The only problem is, all I do is turn the projector off and back on and voila, problem solved.

I do not notice anything during normal viewing that could be called "dithering".

Is it possible that those with LT150's experiencing this (and it doesn't sound like everyone) have a defective or malfuntioning DMD and/or color wheel?

Does resetting the projector help?

As far as the "Matrix" effect goes (is this effect in "The Matrix?") I am not really sure what you guys are referring to.

Have you tried "Video2000", the video system check located at http://gamershq.madonion.com/download/?video2000.shtml ?

I believe one of the tests (the swinging pendulum test) checks for something like this. I don't see it during this test, it would be interesting to see how the LT150's score on the pendulum test...



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Robert Clark

See our home theater (with very poor quality pics!)
http://albums.photopoint.com/j/Album...874&a=12744078


[This message has been edited by Robert Clark (edited 09-10-2001).]


[This message has been edited by Robert Clark (edited 09-10-2001).]
 

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Discussion Starter · #7 ·
Robert, I think Frode has already checked the LT150 out with that test - he suggested I do it quite awhile back, but I could never get it down loaded properly - just hopeless when it comes to ths stuff.


I went looking for the Matrix using my HTPC this evening, but didn't really see any - (Jurassic Park, Toy Story, Conspriacy Theory and Red Planet). I feel a little better. I now need to do it again with another of my little projectors to see if there is a difference between them.


By the way, the only time I think I have seen dithering was with my Marantz - sometimes like the Davis it would go "funny" when switching between normal and dynamic settings and would look like the psychedelic photography from the late 60s. I would have to switch it back to another setting and it would be O.K. I know what I want to be when I grow up - a projector psychologist. http://www.avsforum.com/ubb/smile.gif


Cheers,


Grant
 

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before when i would run across you guys mentioning the "matrix' effect, i had in mind some kind of grid/pixel/ screendoor effect.

but what Bob just described is really close to what i saw in the 'recording studio scene' in Phantom of the Paradise.

as the camera panned across a wall of dials and cabels, etc it was like they staggared...very much like the effect of a mouse cursor.

thats the only time that particular 'problem' has been that severe. just about all the panning i see is somewhat herky-jerky...not creamy smooth by any means, but then that was something i noticed on my RP also...although maybe not to the same extent.

something i have noticed that no one else seems to see or be bothered by ( not that i am, just thought some of the more anal in the audience may be interested) is that in some pans the screendoor becomes very visible in some are of the screen. not across the whole screen, mind you, just some bit of it.

all this kind of makes me think of a guy who loves his wife.

she's a good talker, is supportive, and has a great sense of humour, and can get dressed up to kill ( or at least maim), but when he sticks his nose in her face he realizes she has very large pores and a noticeable hairline over her lip from 2" away. now when he's across the room, at a party and looks over at her, thats all he sees, and he can't figure out why the group of men laughing and mac'ing on her aren't bothered by this.
 

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That's a brilliant metaphor, ckolchak. Just brilliant. Since 1999 when I started reading this forum there have been two. First KBK's mention of the "Dancing Bear Syndrome" and now yours. http://www.avsforum.com/ubb/smile.gif


I sometimes get more entertainment from reading the words of those who participate in this forum than I do from professional entertainers.


Bob


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~ The Sultan of Cheap ~
 

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Quote:
Originally posted by RobertWood:
When the matrix artifact appears, panning objects look just like your cursor does when you have "pointer trails" turned on in Windows. And when the object stops panning, the matrix then disappears exactly like your pointer trails do.
Hi Bob,


Thanks for the detail description. Now I know what you means. Yes, of course I saw such artifact! On the surface, such a mess of blur and splotchy looking does look like a "matrix" effect as Grant said. But look closely. It's actually a combination of "dithering" AND "crosshatching" happens around object edge. If you try hard, you'll see the real face of the "matrix" which is made up with "dithering" and "crosshatching".


Btw, if you're not running the LT150 at it's native 1024x768, then the projector internal scaling artifact will take a role in this "matrix" effect too.


regards,


Li On


PS: Grant, do you run the LT150 at it's native resolution (1024x768) with a HTPC/scaler or just run 480p progressive to it? If you only use 480p connection, do you bother by the LT150 scaling artifact or the scaling artifact visible from your viewing position? Because you know, maybe we just see things differently...
 

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I tend to think that Grant's "matrix/blurring" and Li On's and my "dithering/crosshatching" are one and the same. But it's hard to tell when people notice different things and even describe the same thing in different ways.


I do know that the crosshatching can just be seen as a blurring if you move a bit away from the screen, and if you move even farther away you won't notice it at all.


Also, the temporal dithering is present on both SVGA and XGA single-chip DLP's, so I'm not sure what to make of reports that the Seleco 200 differs from the 250.


From what I understand, there simply isn't anything that can be done for the temporal dithering, since it's purposely built into the digital processing for the DMD. I'm not spending much time thinking up ways to minimize or hide it, since I don't think that can be done. Or, if it can be, then the artifact that you're talking about isn't temporal dithering. No big deal for me, since it doesn't bother me at all. I'm just enjoying my little projector. -- Herb
 

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At the panning scenes, there are two effects from single chip DLP projectors:


(1) Cross-hatching

It normally appears in the background where it is out of the focus. As the camera is panning, the pixels become large and visible to form the cross-hatching pattern. It is easier to find if the area with the same colour is large.


(2) Dithering

It normally appears on the faces (gradient pattern). As the camera is panning, the colour contours appear. It likes displaying a true colour photo at an 256 colours monitor.


Both effects disappear as the camera is stopped. If the panning is very slow, they don't appear. SVGA plus 6 segments colour wheel can't solve this defect.


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CKL
 

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Quote:
Originally posted by hsitz:
I do know that the crosshatching can just be seen as a blurring if you move a bit away from the screen, and if you move even farther away you won't notice it at all.
Hi hsitz,


Thanks for the reply. My poor English really don't allow me to write what I feel and see. I can direct people to check some DVD scene for the "dithering" effect on flesh tone but the "crosshatching" is really hard to tell people exactly where to look for. Now I knew what it is and I saw the "crosshatching" effect frequently!


During one of the test I done at a friend's place, ALL people in the room saw the "crosshatching" effect in one scene. The picture shows a forest and there's a large green leave cover 50% of the image. The large leave is out of focus (the focus is in the background forest) so just looks one large green color object. Then the scene starts to pan, ALL the 6 people (some besides the LT150, some behind the LT150) shouted out and said something was wrong about the picture. Sure enough, the whole large green leave panning on the screen was cover with "crosshatching"! We all laughed! How sad!


regards,


Li On
 

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Hi Grant,


It's NOT THE MATRIX! hsitz in this thread http://www.avsforum.com/ubb/Forum10/HTML/008541.html gave THE EXACT description of the motion artifact effect.


I quote:

Quote:
Originally posted by hsitz:
Hmmm, I think it's probably best not to say that, since TI themselves explains that temporal dithering is an artifact of digital processing in all single-chip DLP projectors.


For people who haven't been able to see these artifacts (and who want to see them) you might try getting up within a foot or two of the screen while there is a single object moving against a static background. Try to see if you can see the pixels making formations that look like "crosshatching" on the moving object, or, if the moving object is a single solid color, look for dithering on it. You should be able to see it. It is present most of the time when there's movement in a scene, although like most people have said, it's impossible to make it out at ordinary viewing distances.


It's not like this temporal dithering is the result of a flaw in the projectors. Rather, it is the conscious result of a design decision by TI. (Albeit a design decision that Li On might question, though I wouldn't.) Most people can obviously live with it, and in fact never know that it's there. -- Herb



[This message has been edited by hsitz (edited 09-01-2001).]
hsitz, if you're here please read. Your description describes THE EXACT motion artifact I saw on the LT150. Not only there is "dithering", but also this strange "crosshatching" in the background when the picture moves.


ALL 1-chips DLP projector users, if what you see don't match hsitz's perfect description of the motion artifact, you're NOT seeing the same artifact as I saw.


On the LT150, I'd said the artifact is 60% dithering and 40% crosshatching. On the Seleco 200DM (848x480/800x600 dual formats), it was 30% dithering and 70% crosshatching. On a Plus Piano (848x480/800x600 dual format) I saw, it was 50% dithering and 50% crosshatching. After I pointed out the motion artifact on the LT150 to a friend, he said he saw the exact same artifact on a friend's Plus 880 (800x600) before.


Again, it's NOT THE MATRIX. As for the upcoming THE MATRIX -the sequel, (the movie I mean) I'm looking forward to have it on DVD...


regards,


Li On
 

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