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HD Projector Distortion - Horizontal Banding

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Old 12-27-2005, 11:05 AM   #1
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Default HD Projector Distortion - Horizontal Banding

Very annoying problem that I need help with:

In a nutshell, when very dark scenes are displayed in DVD playback, there are noticeable static horizontal ghosted lines on the image. I am using a Panasonic PT-AE700U projector with component video cable connections. I have used a 100-ish$ Toshiba progessive scan dvd player and also a 70-ish$ Panasonic progressive scan dvd player, I have seen the lines when using both units.

The lines are thicker towards the top of the screen, getting thinner towards the bottom, they do not move at all, they stretch the entire width of the screen, and are translucent gray in color compared to the black background on which they are usually seen.

I switched the DVD player from Progressive Scanning to Interlaced Scanning and two things happened: first of the all, the image was not quite as bright...not a problem I suppose, but I'm curious as to why, nonetheless, from a technical standpoint. Secondly, the ghosting distortion lines were not present in Interlaced mode. So basically, the progressive scan image is brighter and clearer, but the distortion lines are present in very dark seens. I have tried swapping cables, movies, DVD players; the lines are still there. Is this a familiar problem with cables? Progressive scanning? Projector?

Another weird thing is I can make the lines pretty much go away, but at the expense of brightness. I have the contrast turned to 16 on a
-32 to +32 scale and the brightness to 0 on a -32 to +32 scale. When I turn the brightness down to around -16, the lines are pretty much non-existent, but then the image is not clearly displayed in very dark scenes as it is simply too dark to make details out. The lines are very annoying as they are quite noticeable at the video setting that I like to use.

Another point of interest is that the distortion lines are not noticeably present when video games are being displayed, even in very dark games such as Doom 3 or the like. It only appears to be during DVD playback from what I can tell.

Any help or insight would be greatly appreciated. Thanks alot.
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Old 12-27-2005, 09:56 PM   #2
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It sounds like it's the AE700 since the lines show up with two different DVD players in prog-scan mode. You may want to try calibrating the AE700 with the Digital Video Essentials DVD or AVIA DVD. If there's more than one component video input, try switching the DVD player to the other component input to see if the lines still show up.
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Old 12-27-2005, 11:52 PM   #3
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Maybe it's caused by the same thing that Projectorcentral saw in the AE700 projector -but their's was vertical not horizontal -
http://www.projectorcentral.com/banding_rainbows.htm -a whole article on a very similar subject and they use the AE700 as the example of the problem -.
Quote:
...LCD vertical banding
On occasion, LCD projectors can manifest a problem known as vertical banding. Vertical banding consists of subtle (sometimes not so subtle) vertical bands often in the range of about 1-inch thick, evenly spaced across the entire picture. DLP projectors don't have this problem. Most LCD projectors don't either—it is not an automatic byproduct of the technology. It is a flaw that can occur in the manufacturing process of the LCD panels themselves, and some LCD panels will tend to manifest it more noticeably than others. The panels that cause the most visible problems are usually weeded out in the vendor's quality control process. However, those that create just a hint of banding often pass through QC, since it is prohibitively expensive to discard all parts that exhibit flaws which may have no practical impact on picture quality.
So, we end up with a situation in which some LCD projectors, even within a given production run on one model, will have no banding at all,
some may have a hint of it that does not rise to the level of a significant issue, and some may have a more visible problem that really does impair the enjoyment of the viewing experience. In the latter case, sometimes the problem can be mitigated with internal adjustments made by the dealer or vendor service departments, and sometimes the LCD panels or the entire unit need to be replaced.
.As an example, we have two Panasonic AE700s in house. The older of the two was one of the first units built, and it is the unit we reviewed last fall. We saw some subtle vertical banding on that unit and reported it in the review. It produced some noticeable texture in gray screen test patterns, and in video on infrequent occasions depending on subject matter, but it was not considered to be a significant flaw. In December, Panasonic engineers came to visit, and on that occasion they called up the service menu and tweaked our AE700. The adjustments they made reduced the visibility of the banding on test patterns by about 50%. So a problem that wasn't a big problem to begin with was reduced, but not eliminated entirely, with internal adjustments.
We acquired a second AE700 about two months ago. This unit shows almost no banding at all on gray screen test patterns although it is still detectable. However it is even less visible than it was on our first unit after tweaking. On the second unit, banding is essentially zero with normal video material playing. When we detect it at all, it is because we are specifically looking for it.
Therefore, those who say they see no banding at all on their AE700 are correct, and those who say they've had a problem with banding on the AE700 are also correct. And this phenomenon can occur with any LCD projector.....
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Last edited by maicaw; 12-28-2005 at 12:01 AM.
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Old 12-28-2005, 08:37 AM   #4
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Doesn't sound like the same problem as vertical banding, which was an inherent issue with the earlier LCD engines and would show up regardless of which connection used. VB has now been largely eliminated (no VBs on the AE900). These are lines as oppose to bands.
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Old 12-28-2005, 10:09 AM   #5
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Default just like the old days

Quote:
Originally Posted by borromini
Doesn't sound like the same problem as vertical banding, which was an inherent issue with the earlier LCD engines and would show up regardless of which connection used. VB has now been largely eliminated (no VBs on the AE900). These are lines as oppose to bands.
I just thought since his PJ was the same model ProjCent used as an example of a very similar problem on his model - that could be effectively corrected from the service menu - He might want to contact the mfg about whether he can do some good for his problem using the service menu - the menu access sequence is likely posted along with most others mfgs somewhere on the web- just about every sony TV model service menu access sequence is listed. as are DVD players -
just like the old days - when every grocery store had a tube checker - so you could fix your own TV.
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Old 12-28-2005, 10:13 AM   #6
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I'll do some more research on some of your ideas, do some of the calibrating that you've mentioned, hit it with a wrench a few more times... etc...

Something else very interesting when I was swapping inputs and whatnot:

I used my Xbox360 as an input, went to a very dark image and found no hint of the horizontal lines. I then switched to the older Xbox and went to a very dark image and there were hints of the lines!!! I also hooked up my PC utilizing the full resolution (as is with with the Xbox360) and there were no noticeable lines. The distortion seems to come up when the signal is not HD, but upconverting or displaying a lower than native resolution...

The Xbox was running at 480p, and the DVD player was running at 525p, the Xbox360 was running at 720p. And like I said I did not NOTICE the distortion lines when the DVD player was in interlaced mode, thats not to say they weren't there; progressive mode is much brighter so maybe the distortion does manifest itself noticeabley with the lower light output of interlaced mode. I am going to try it with 1080i on the Xbox360 and see if that looks different than 720p.

Does this spark any further ideas??

I'll post what I come up with when I do some more testing. In the meantime, any other ideas are welcome. Thanks, guys.
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Old 12-28-2005, 10:48 AM   #7
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No further ideas come to mind. The AVS forum link is an extensive resource...I suggest you peruse the thread.
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Old 07-05-2006, 12:28 PM   #8
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Default problem 'fixed'... sort of.

Well, for those interested, I could not get the lines to go away on the 700 series panny PJ. I have since bought a 900 series panny and the problem is non-existant. Problem solved, in a sense, though I would still like to figure out what the deal was with the 700... Maybe it was just that particular unit; I don't know. Thanks for the ideas for those that gave inputs.
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