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How do?


By not transmitting any light. And that's the real trick, to do it as fast as it has to. IOW, on a pixel level (RGB sub pixels) all have to be as fully turned-off as possible. There are entire patents obtained for techniques to accomplish this.
 

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Don't forget reflected light as well.


Phosphor based displays reflect RGB as well as emit it. RGB filters also partially reflect RGB. All this makes true blacks difficult with the lights on.
 

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Quote:
Originally posted by fasteddielv
Ah thanks Thumperboy, that's really helps! NOT!
I think the point is that, with the so many threads, it is difficult to keep up so descriptive titles help tremendously in enabling folk to quickly ascertain whether that thread may help or interest them without having to open every one.
 

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Quote:
Originally posted by fasteddielv
Ah thanks Thumperboy, that's really helps! NOT!
Thumper is absolutely correct. What in the world is so difficult about creating a thread title that actually indicates what the thread is about. I'm sure I'm not the only one who gets annoyed when I open a thread only to find it's something I have no interest in and wouldn't have wasted my time if the thread title actually made sense and was informative.


I'd love to see the day when I and everyone else wouldn't look at threads with meaningless titles. That would put an end to this practice.
 

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Quote:
Originally posted by Jerry G



I'd love to see the day when I and everyone else wouldn't look at threads with meaningless titles. That would put an end to this practice.
I agree and took the appropriate action: I edited the title on the top page


btw- I learned that a thread starter CAN edit the title of a thread on the top page as long as it is done within a few minutes of starting it- otherwise only a moderator can edit it


I think it should be standard practice that meaningless thread titles will be edited by a mod if he deems necessary


:D
 

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Back to the subject at hand. I too often wonder about this. Seems like its a pretty complicated process. For instance, when watching with black bars on the side (which I rarely do), those are inherently blacker than the dark ares of the picture. I am sure that has something to do with the black level of the scene though. But my question is how does a plasma actually show shades of black? Seems to me like it would either be black (like the black bars) or not black. But aren't their various shades of black, like in a night sky scene?


Just wondering.


E. J.
 

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Quote:
Originally posted by xrox
Don't forget reflected light as well.


Phosphor based displays reflect RGB as well as emit it. RGB filters also partially reflect RGB. All this makes true blacks difficult with the lights on.
Thanks Mark- Now that title looks good.


Good point xrox,


Two approaches to limit reflected light include the black line masking at barriers boundaries, and the filters used in the front lens to limit outside light penetration.
 

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There are shades of grey, not shades of black per se.


But it's hard efjiii to do that well because it is a series of subtle states that are nearly black, but not quite.


I have long found one shortcoming of the Panasonic is that the black is black, but the very dark greys also look too black to distinguish... Poor "shadow detail".
 

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Discussion Starter · #14 ·
OK, OK. I will never start a thread with a meaningless title. I will never start a thread with a meaningless title. I will.......500 times.

It did get over 100 hits though.


So the answer basically is per Brucer.

By not transmitting any light. And that's the real trick, to do it as fast as it has to. IOW, on a pixel level (RGB sub pixels) all have to be as fully turned-off as possible. There are entire patents obtained for techniques to accomplish this.

Anyone want to add to this?


Eddie
 

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ejfiii,


Plasma use subfield firing to show greyscale. Shades of black/grey are just low level white-greyscale. In other words all three subpixels are firing at low level to produce R+G+B = white at low levels.


If I remember correctly, during black periods, each plasma cell is not turned off but is kept at a very low level of ionization because it is much more efficient power wise as well as faster to switch greyscale levels.
 

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MikeSer,


Cool, do you have more info?


I'm sure every company has some fancy new addressing technology that we know little about. I don't know as much as I would like to about plasma cell adressing.


I rarely see any papers in the SID journals I read that are about black levels in plasma.


Maybe I'll look over them again and see what I can find and then post here.


Cheers
 

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Well here's some light reading for you:


U.S. Patent # 6,603,447


Method of driving AC plasma display panel

"In the above operations, with respect to a discharge cell that is not operated to emit light, the initialization discharge occurs in the initialization period, but the write discharge, the sustain discharge, and the erase discharge are not caused. Therefore, the wall voltage at the surface of the phosphor 10 on a data electrode Dh (other than the designated data electrode D.sub.j ) and the wall voltage at the surface of the protective film 5 on the scanning electrode SCN.sub.i and the sustain electrode SUS.sub.i that correspond to the discharge cell that is not operated to emit light are maintained in the state at the end of the initialization period.


A series of operations in the initialization period, the write period, the sustain period, and the erase period are set to be one subfield, and one field for displaying one picture includes, for example, eight subfields. The luminance of light emitted from discharge cells to be operated in those respective subfields is determined depending on the number of applications of the sustain waveform. Therefore, by setting the respective subfields to have the number of sustain waveforms in the ratio of 2.sup.0 :2.sup.1 : 2.sup.2 : . . . : 2.sup.7, a display having 2.sup.8 =256 shades of gray can be carried out. Thus, images can be displayed in a television receiver, a computer monitor, or the like.
"


Not sure where the IBM connection comes from, as there as literally hundreds of very specific "Methods of driving AC plasma display panel" patents held by Matsushita (assignee name).
 

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At every pixel there is a dark sucker (or, more correctly: darkness sucker).


To create bright areas, the dark suckers suck away all of the darkness.


Currently, dark suckers, when active, require a minimum voltage to idle. This means that they always suck away at least a little bit of the darkness.


To achieve 30fps playback speeds, it is not possible to turn the dark suckers completely off when a pixel is black. The transition time is too long. If the dark sucker could be completely deactivated, the problem would be solved.


Manufacturers are pursuing two strategies to relieve the problem:


1) Improve the dark sucker idle behavior, to stay active with lower idle voltages.


2) Develop a corresponding light sucker, which can be paired with each dark sucker. The light sucker will eat the small light output from the idle dark sucker. The trick is to stop the light sucker from ruining the overall brightness of the display.


While the theory of this is taught in undergrad physics courses, the application is nontrivial.
 

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I have the Panny 6UY. When it is turned off the screen is not black, it is a dark (OK very dark) grayish greenish color. Is this the blackest black that this plasma can achieve? In operation, the blacks definitely look blacker than that (the plasma turned off state). In fact they often look about as dark as the black border on the glass (not the black bezel, the border on the glass). Or is this an optical illusion meaning, that is, am I simply perceiving that it is blacker than it really is.


John
 
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