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Unit is in "on" position. Does either type of display draw "full current" even when no video signal s being sent to the display?

Do displays that contain a lot of white in them draw more juice than mostly black scenes?



Thanks.



...mike
 

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Plasma's draw more light when displaying a full white screen than when displaying a full black screen. LCD's depend on the type, if the backlight is of the dimming variety then the same applies, but if it is a old fashioned non dimmable then there should not be a major difference. That is to say old fashioned LCD's should draw full power as long as they are on.
 

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The short answer is YES, flat panels of both types draw power when ON regardless of whether they are displaying an image or not. Some portion of the power consumption is reduced by dimming the brightness on a plasma or reducing the backlighting setting on an LCD screen.


Even when they are turned OFF, HDTVs use a small amount of power (standby power rating) to enable them to respond to a remote control.
 

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Standard LCDs use about the same amount of power regardless of what is on the screen, those bulbs are always on. Plasmas modulate the power consumption, more on bright scenes less on dark.
 

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The terms you are looking for are:

Power on Demand (CRT,Plasma,OLED,SED,FED.....or any display which "generates" light within individual pixels or dots)

Constant Power (LCD with the exception of Local or Global dimming backlights)

Display Power Characteristics


Regarding Plasma displays: The black level glow (MLL) that you see on a completely blank screen is due to the requirement to keep the pixels primed with charged particles even when not displaying an image for a lengthy period. This process obviously draws current and thus generally determines the mimimum power consumption of Plasma displays.


However, with recent advances in materials and cell driving methods, most modern Plasma displays are now able to turn off all current to the pixel array when no signal is present. I know that Pioneer 9G Kuro models will turn off all power to the pixel array after 15-30 sec of no signal or black signal. I think Panasonic NeoPDP models also do something similar.


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Without disagreeing with xrox, many modern LCDs also support advanced power saving modes and can also cut off the backlight after X minutes of no signal. Finally there are video sources such as the PS3 and some PVRs that automaticly drop into a dim mode after X minutes with the image paused, which also saves power.


On my 2007-vintage Samsung (a conventional "Constant Power" device by the definitions above) setting the Power Saver mode to "Auto" will extinguish the CCFL backlight after one minute of no video. I don't like it and don't use it - the CCFL startup takes 5-7 seconds to complete and you can miss that much program before the screen lights up.


Plasma startup times are also non-zero - if Plasmas cut off their cells entirely, it must be by shutting off the high voltage supply - which would seem to cause the same problem as the LCD startup I complained about.


I also don't like Dynamic video modes on any LCD or Plasma I ever used, because it's impossible to accurately calibrate the picture with this feature. Dynamic modes vary the white levels and black levels both, not very usefull if you are attempting calibrated images. But Dynamic video does also save power on the average. Many of the new Plasmas have the Dynamic mode now, it used to be found only on LCDs, but I never use it anyways.


Edit: Too bad that aggressive Power Saving features often are in conflict with optimum video quality. But as long as the menu lets you defeat the feature if you wish, I won't complain.
 

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Gary, as is seems your post is responding to mine (I'm not sure), I would point out that the portion of my post mentioning plasma being able to turn off the power completely was an aside of technical interest and not really addressing the OP. Simply put, conventional LCD are constant power and will be at max power (for a given BL setting) even at zero APL or no signal. CRT, Plasma, and LD-LCD will be at minimum power under the same conditions. Shutting off after a few minutes of no signal is a separate story. In the case of power shut off techniques LCD goes from max power to zero while Plasma will go from min power to zero.

Quote:
Originally Posted by Gary McCoy /forum/post/17055818


On my 2007-vintage Samsung (a conventional "Constant Power" device by the definitions above) setting the Power Saver mode to "Auto" will extinguish the CCFL backlight after one minute of no video. I don't like it and don't use it - the CCFL startup takes 5-7 seconds to complete and you can miss that much program before the screen lights up.

Are you implying that because the CCFL can shut off after a few minutes of no signal it is not a constant power display? If so you fail to understand either the terms or the differences in technology?

Quote:
Originally Posted by Gary McCoy /forum/post/17055818


Plasma startup times are also non-zero - if Plasmas cut off their cells entirely, it must be by shutting off the high voltage supply - which would seem to cause the same problem as the LCD startup I complained about.

Plasma displays were not able to shut power off because the discharge delay would become too long, and discharge probability would become to small to maintain a picture. New cell designs enable high discharge probability and short delay even when the cell has been off for a long period. This is also the technology that enabled the Pioneer ECC prototype.

Quote:
Originally Posted by Gary McCoy /forum/post/17055818


I also don't like Dynamic video modes on any LCD or Plasma I ever used, because it's impossible to accurately calibrate the picture with this feature. Dynamic modes vary the white levels and black levels both, not very usefull if you are attempting calibrated images. But Dynamic video does also save power on the average. Many of the new Plasmas have the Dynamic mode now, it used to be found only on LCDs, but I never use it anyways.

Plasma displays dynamic white (ABL) is a high apl feature which is not what we are discussing here? Fundamentally, dynamic white on a Plasma should never change the black level. On an LCD, dynamic white will always fundamentally shift the black level.
 

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xrox, I wasn't disputing what you said, and I viewed the slide set you linked to and I thought it was very informative. I was just elaborating by describing some of the assorted power saving features that alter the simple distinction between constant power displays and others.


I'll take your word about the difference with Plasmas that have dynamic video modes, I have not owned a plasma in 2+ years. But I do have two LCDs and can't successfully calibrate either unless I use a mode other than dynamic.
 
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