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Discussion Starter · #1 ·
"We see no hint of any vertical banding on our test unit. However the Z3 has an LCD panel adjustment mechanism available through the menu to tweak away the artifact if it should show up."


It sounds like vertical banding has been identified as a type of panel misalignment. This is a quote out of Projector Central's review of the new Z3.


Can anyone tell me if this is true? Or am I misreading the statement?


I screwed with my settings on my old LCD and caused vertical banding once, and kept fooling with it until I fixed it. But I was such a hacker that I didn't figure out what I had done. So I have seen that some adjustments help, I just don't know what they are. In my case, it WASN'T panel alignment.


PS: I will argue that this statement/topic/issue applies to all our LCD players so it isn't in the wrong forum just because the Z3 was involved.


And sorry for the fake subject line, but I wanted to grab enough readers to get the straight skinny. Sorry.
 

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Vertical banding is not caused by panel misalignment. I believe it's related to the difference in, what should be identical, voltages that is applied to a given vertical set of pixels on the panel.


The Z2 had a similar service menu adjustment that aleviated the VB but unfortunately, was not a cure.


I am assuming the Z3 is the same thing.
 

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Joe - pocoloco's explanation agrees with my understanding. The Epson's have a similar adjustment, and I have yet to get one with VB (I'm on #3 now...). Lots of FPN, though.


So, if you have a good LCD, then it's a function of the drive electronics being in sync, as it is anything to do with the physical properties of the panel itself (of which I'm aware...).


Later,

Bill
 

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It's definately voltage.



It's impossible to think that panels could be misalligned so perfectly every time;)
 

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I spoke directly to someone who sold X brand projectors..and not a single one ever came with vertical banding issues. New model comes out from same company.


Prices are pushed through the floor.


Every single one comes out of the box with vertical banding. He has opened over 50 boxes so far.


Do you still want that ultra low price?


Think again.
 

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Quote:
Originally posted by KBK
He has opened over 50 boxes so far.
Surely there's an easier way around MAP?? ;)


Later,

Bill
 

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I think KBK makes a good point. Are manufactures forced to cut corners because prices are pushed so low?
 

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nonsense. ALL LCDs exhibit vertical banding. BUT can be fine tuned so as to hide it very good.
 

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Discussion Starter · #9 ·
So what "fine tuning" makes all the voltages for all the vetical lines the same? That seems like something that should always be the same. How did they make electronics that had the capability of sending a different amount of voltage to each vertical line? Sounds like someone had to invent a way to screw this up.
 

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Wrong end of the argument. If the voltages are all the same you get banding. They need to be tuned to slightly different voltages to eliminate it.


BB
 

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"Sounds like someone had to invent a way to screw this up."


The pixels' and driving transistors' electrical characteristics are determined in part by their physical dimensions. Expecting the etching process to result in dimensions uniform to the submicron level is not realistic.


The beauty of DLP is that even if the mirrors' reflectivity varied by several %, you wouldn't see it.
 

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Quote:
Originally posted by noah katz
The beauty of DLP is that even if the mirrors' reflectivity varied by several %, you wouldn't see it.
I suspect one would notice several % variation in mirror reflectivity just the same as several % variation on LCD transmissivity or LCD drive voltage.


There are couple of things working in DLPs favour however:


(1) It is probably very easy to achieve high uniformity of reflectivity during manufacturing. And it's not like the reflectivities have to match over all brightness levels in the same way that transmissivities have to for LCD - there is one reflectance and that's it.


(2) If we discount flip times, the mirror positions are effectively binary (on or off). Also, pulse width modulatio, not mirror reflectance, is used to determine brightness. Therefore DLP is truly digital. There is no notion of a conversion of the digital input signal back to analog to control brightness in DLP the way there is in LCD.


Because it is (effectively) fully digital, DLP is not susceptible to component tolerances (either in the cells themselves or the drive electronics) the way LCD is.


Brent
 

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JHouse, there are 2 service menu items in the PLV-70/20HD to lessen the effect of banding/FPN.
 

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Joe, you sober, dude?
 

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Discussion Starter · #15 ·
Quote:
Originally posted by Brandon B
Wrong end of the argument. If the voltages are all the same you get banding. They need to be tuned to slightly different voltages to eliminate it.


BB
Is this because of what Noah said? i.e. you have to compensate for the physical differences that lead to voltage/electrical differences?


Otherwise, I don't get how different voltages would eliminate the banding. Or what the real cause of it is.


Ferret,


Barely.
 

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The way I understand it, and I read about this some time ago so I apologize if I'm a little off:


In order to keep the liquid crystals from developing a "memory", they periodically reverse the polarity of ON/OFF. They do this by swapping the polarity of the driving voltage. The rows (not single pixel rows, but the multiple pixel rows you see in VB) are alternating polarity, so when row 1,3,5,7...etc are positive rows 2,4,6,8...etc are at a negative voltage. Because the characteristics of the crystals may not be completely symmetrical, you get some light intensity variation from positive to negative.


Think of it as if you had two separate panels interleaved. You would have to calibrate the two sides to match, even though they theoretically should produce the same light output for a given voltage.
 

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Then how would one explain the vertical banding becoming visible 45+ days after I first purchased the unit?


I have a Z2 PJ that I purchased end of August, and only recently has the vertical banding become visible...
 

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We need to kidnap an LCD panel engineer. Bring him to Alan. And then make them talk.
 

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Quote:
Originally posted by Brandon B
Wrong end of the argument. If the voltages are all the same you get banding. They need to be tuned to slightly different voltages to eliminate it.


BB
Incorrect!


If you want to put up a uniform solid colored screen you want every pixel to get the exact same voltage. If there are vertical rows of pixels that are either getting a higher or lower votage you will see banding.
 

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Has anyone with VB tried a hard shut down of their PJ by unplugging it to see if it disappears after reboot?


There is a rumour going around that this works.

Here is a quote from the
 
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