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Panasonic 2010 plasma: Floating blacks

305K views 2K replies 317 participants last post by  Majcric 
#1 ·
Floating Blacks:


I purchased a TC50G20 from Best Buy on March 6th. I also purchased their new Panasonic Blue Ray player. The THX setting mode out of the box is gorgeous. But wait, there's more.. The first blue ray I viewed was the Matrix, 10th Anniversary Edition. I loved this G20 until I saw the gamma levels change 4 times during the scene when Trinity rolls down the stairway and aims her guns up at the window. I also noticed the same "lightening and darkening" of the screen while watching a scene from Pirates 3 between on the ship at night.


I can rewind and watch it over again and can see it every time. This drives me nuts. What's frustrating is that the gamma/brightness shift is not simultaneous with the scene changing: the set takes a moment to adjust to the frame in the movie. This occurs even with the CATS setting off. A darker scene in the movie with more blacks causes the set to adjust and the blacks become "darker" a few moments later. It is so obvious that I am not able to watch blue rays in the dark at this time, and I'm even considering returning the set. Call me picky, fine. But I'm not happy about this issue. After tinkering, I realized that the shift is less evident when the set is watched on the "dark" setting found in the advanced menu. Also, on the "custom mode" set up, I can set the gamma to 2.6 on the pro menu and eliminate the problem. The downside with both these settings is I lose grays and contrast. No one I've spoken with at Panasonic even knows the difference between infinite black and infinite black pro, let alone what floating blacks are, really?


My question: Is there any way to fix or lesson this change? What causes floating blacks? Is this a power issue? Is it a tech issue? What alternative do I have other than the new Panasonic 2010 Plasma line to get great blacks? Will the v-series have this issue with the infinite black "pro" panel? These are my questions. Yes, I have adjusted the brightness multiple times and no fix. Any help will be appreciated.
 
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#1,179 ·

Quote:
Originally Posted by ericzuellig /forum/post/19608430


Iam geting really bad IR in like 1 to 2 min on my vt. If I pull up the menu for for 30 50 secs iam geting bad IR same with tv shows 5min of larry king tons of IR I have other panasonic tvs that do not do this. 1080P load logo is on for 20sec on the bluray load screen and i see the IR on the black bars when letterboxed. It does not go away until I run full screen.

My S2 is same or maybe even worse. Even 5 seconds of the on-screen menus or my Onkyo AVR's splash logo gets retained (Cinema Mode with moderate contrast). Reports on IR susceptibility in '10 Panny plasmas seem to vary widely - some have it bad like ours... others have worked at it and can't induce any.


I'm not too concerned because the IR goes away just as fast.
 
#1,180 ·

Quote:
Originally Posted by ericzuellig /forum/post/19608430


Iam geting really bad IR in like 1 to 2 min on my vt. If I pull up the menu for for 30 50 secs iam geting bad IR same with tv shows 5min of larry king tons of IR I have other panasonic tvs that do not do this. 1080P load logo is on for 20sec on the bluray load screen and i see the IR on the black bars when letterboxed. It does not go away until I run full screen.

Are you in "torch" mode?
 
#1,181 ·

Quote:
Originally Posted by Dayton /forum/post/19608536


Are you in "torch" mode?

Can't answer for Eric, but mine certainly is not.


It takes just seconds to retain an image. If the final seconds of a scene before a commercial break are relatively static, you can see most of that scene in the fade thru black going into the commercial. Even a minute of SportCenter on ESPN and you see all of the their graphics very clearly in the black screen. If I fire up my system but send it to a dead input or channel, the initial Onkyo splash and the Panny HDMI1 banner are clearly visible on the black screen after only a few seconds of exposure... but, as I mentioned previously, they disappear just as quickly with live video.


The Panasonic authorized tech that did an unrelated repair on mine said it was the worst IR he had ever seen.
 
#1,183 ·
FLOATING BLACKS EXPLAINED


Post created as a place to compile information describing the cause and reason for floating blacks. So far 4 patents describing the issue (aka – feature) are posted. The post is linked in the Zero Black Thread .

Brief Version

Effect - Black level changes depending on APL of screen (APL=Average Picture Level))
Cause - The number of all-cell initialization pulses are changed depending on APL
Reason - At high APL the panel impedence causes a voltage drop (due to higher current) and pixels may start to misfire so an additional all-cell initializatin is peformed to compensate (re-priming the cells)
Why Only Panasonic - Other manufacturers just raise address voltage or width to compensate which impacts panel efficiency



Detailed Version


The phenomenon we see is an abrupt change in black level depending on the content on the screen. This is especially noticeable in black bar areas and while watching in low ambient light.


Below is some definitions to know before reading the patent literature.
  • APL is the Average Picture Level (think of it as the % of the screen at full white)

  • Initialization is the process where the pixel cell is prepared for stable operation (discharged in order to produce priming electrons (think “pre-discharge”) and discharged in order to create wall charge)

  • All-Cell Initialization is when every pixel is initialized regardless if they are to be used or not (main contribution to black level)

  • Selective Cell Initialization is when only cells to be used to emit light are initialized (no contribution to black level)

  • Discharge start voltage is the voltage threshold at which discharge occurs above this voltage and no discharge occurs below this voltage.


Description of Panasonic REAL BLACK DRIVE (Panasonic)
  • 1 or 2 "all cell" initialization periods (every subpixel is initialized no matter what) depending on APL.
  • All other subfields use "selective" initialization periods (only pixels that have previously generated a subfield)
  • see end of post for more detail

Panasonic Patent application # 20090021452 (same patent that describes rising blacks)



Describes how the black level will shift at 6% APL (becomes darker below 6% APL and brighter above 6% APL). Notice the one large single pulse (initialization) for the 6%APL case.




Patent also says that if a hysteresis characteristic is applied there will be two thresholds at 5% and 7% that will lessen the number of black level shifts. Black level become higher above 7% APL (2 all-cell initializations used) and then become darker below 5% (1 all-cell initialization used).


The patent does not clearly state the reason it is necessary. The patent does seem to suggest that the intended feature is a stable picture with higher contrast at lower APL (where it is important). The perceivable brightness shifting is an unwanted byproduct.



Panasonic Patent application #20100253673


Describes the use of a combination of no initialization ( ZERO BLACK l) and REAL-BLACK-DRIVING (all-cell and selective cell initialiation). More specifically at least half the frames will be displayed by using no initialization (zero black) and the other half displayed by REAL-BLACK (1 initialization+selective initialization). To overcome stability issues with this method they change the address pulse width based on the ratio of zero black frames and REAL-BLACK frames used.


But if you read claim 3 you see that the ratio of these two methods is changed based on APL which again will create floating black levels.


The patent does seems to finally describe WHY floating blacks is required on Panasonic designs.
Quote:
Originally Posted by Panasonic Corporation patent application #20100253673 /forum/post/0


[0118]Next will be described the reason why insertion ratio N of the selective-cell initializing field is determined according to APL in the third embodiment.

[0120]Image display with high APL generally allows the image display area to have an increased ratio of sections to be lit, which also increases the ratio of the discharge cells that undergo the address discharge, and accordingly, increases discharge current generated in the address discharge. The circuits that drive electrodes and the electrodes themselves have impedance, and therefore increase in discharge current causes a voltage drop. Due to the voltage drop, voltage to be applied to the discharge cells decreases, by which discharge delay increases. Extending the scan-pulse width required for address discharge compensates for the increase in discharge delay.

In easier to understand terms the panel has resistance and thus when a lot of pixels are lit (aka – high APL) the voltage drops closer to the discharge start voltage (see definitions start of post) . When this occurs the discharge delay goes up and the discharge probability goes down. The pixels may start to misfire. To compensate for this the panel uses an extra all-cell initialization because it provides extra priming particles that lower the discharge start voltage to a value that compensates for the voltage drop described above.

Figure 11 from the patent - see description below

FIG 11 description : Think of the vertical axis as the time (address voltage pulse width) required to achieve stable addressing. And the horizontal axis as the time after all-cell initialization. Curves 1101, 1102, 1103,1104 all describe how the longer the panel goes without all-cell initialization the more time (or voltage pulse width) required to ignite it stably again. Now the different curves all have the same slope but represent different APL.
  • 1101 – measured at 100% APL
  • 1102 – measured at 50% APL
  • 1103 – measured at 18% APL
  • 1104 – measured at 1.5% APL

You can see that the higher the APL goes the more address voltage width is required to achieve stable operation (as per reason described above).


Panasonic patents 7446734 and 7583240


Describe floating blacks in a 600Hz system using up to 5 black level shifts depending on APL.


Remember that the initialization step produces black level. More initialization the higher the black level. And APL can be thought of as % of the screen at full white. Check this out:






Reasoning (pay attention to bolded areas)
Quote:
Originally Posted by Selected paragraphs from Panasonic patents 744673 and 7583240 /forum/post/0



As described above, in this exemplary embodiment, because it is considered that there is no or a small area displaying a black picture when an image having a large APL is displayed, the number of all-cell initializing operations and thus priming are increased to stabilize discharge. In contrast, when an image having a low APL is displayed, it is considered that there is a large area displaying a black picture. Thus, the number of all-cell initializing operations and the black picture level are reduced to improve black display quality. Therefore, at a low APL, luminance in the area displaying a black picture is low, and an image having high contrast can be displayed even when the image has areas having high luminance.


In the all-cell initializing operation, it is necessary to cause initializing discharge using the scan electrodes as anodes and the sustain electrodes and data electrodes as cathodes. However, phosphors having smaller electron emission factors that are applied to the data electrodes may increase discharge delay in the initializing discharge using the data electrodes as cathodes, thus causing unstable initializing discharge in some cases.


Additionally, considerations are given to increasing the partial pressure of xenon in the discharge gas filled into the panel to improve the luminous efficiency of the panel. However, an increase in the partial pressure of xenon destabilizes discharge, especially initializing discharge. This unstable discharge poses a problem of writing failure in the subsequent writing period that is caused by a narrower margin of the driving voltage in the wiring operation.

With recent higher definition of a panel, the number of discharge cells is increasing and the period of time used for writing operation of one discharge cell is reducing. In addition, to improve image display quality, such as improvement of dynamic false contour, writing operation at higher speeds, such as discussion on a driving method for increasing the number of sub-fields, is required.


Now, the all-cell initializing operation for initializing all the discharge cells serves to form wall discharge necessary for writing operation, as described above. The all-cell initializing operation also serves to generate priming (priming=excited particles) to reduce discharge delay and stabilize writing discharge. Therefore, for stable high-speed writing operation, a method of increasing priming is effective. However, simply increasing the number of the all-cell initializing operations increases black picture level and decreases contrast, thus deteriorating image display quality.
Detailed description of Panasonic REAL-BLACK-DRIVE (as best as I currently understand)

All Cell Initialization:

-first creates excess wall charge state on all cells to [Q4]

-then downslope depletes wall charge in all cells to a normalized low level of [Q1]

- [Q1] is considered the "off" state (at this point all cells are at Q1)

Address Period

- scans all subpixels line by line increasing wall charge in selected pixels to [Q3]

- [Q3] is still below the discharge start voltage

- [Q3] is considered the "on" state while all other pixels with low levels of wall charge are still in the "off" state of [Q1]

Sustain Period

- applies AC voltage that discharges only the cells in the "on" state of [Q3]

- leaves the cell in the "on" state of [Q3] when completed

Selective Initialization

- Only the cells in the "on" state (whith high levels of wall charge) are depleted back to [Q1] using the same downslope voltage ramp (see first plot) while all other cells are already at [Q1] and thus are unchanged during this step

- the panel wall charge is now normalized to [Q1] and again ready to be addressed
 
#1,185 ·
If putting a light in front of the CATS sensor puts the TV in an always bright ambient light...


I'm just thinking...


What if you remove the sensor?


Not putting a tape, but actually removing it. I think the sensor is catching light from the panel itself (the panel is too bright and the inside of the TV gets too much light as so the CATS sensor) and that's why the floating blacks issue no matter if it's on/off and there is no light on the room... just a thought.
 
#1,186 ·
(50VT25 less than 2wks old)

I think I experienced my first issue with the Floating Blacks, if the rapidly rising and falling of the contrast/blackness of the screen is what it is referring to. The recent episode of Community - "Abed's Uncontrollable Christmas" the whole episode is in stop-motion animation. In several scenes the TV kept getting lighter/darker. Drove my wife mad.


I've sent an email to Panasonic about the issue and have a case #, but need to follow up with a phone call. My first use of the plasma was the break-in slides, D-Nice's user settings AND service menu settings. My worry is that I've messed with the service menu. Is this going to cause a problem with the warranty?
 
#1,187 ·
Quote:
Originally Posted by nick burns
(50vt25 less than 2wks old)

i think i experienced my first issue with the floating blacks, if the rapidly rising and falling of the contrast/blackness of the screen is what it is referring to. The recent episode of community - "abed's uncontrollable christmas" the whole episode is in stop-motion animation. In several scenes the tv kept getting lighter/darker. Drove my wife mad.


I've sent an email to panasonic about the issue and have a case #, but need to follow up with a phone call. My first use of the plasma was the break-in slides, d-nice's user settings and service menu settings. My worry is that i've messed with the service menu. Is this going to cause a problem with the warranty?
no.
 
#1,188 ·

Quote:
Originally Posted by Nick Burns /forum/post/19634155


(50VT25 less than 2wks old)

I think I experienced my first issue with the Floating Blacks, if the rapidly rising and falling of the contrast/blackness of the screen is what it is referring to. The recent episode of Community - "Abed's Uncontrollable Christmas" the whole episode is in stop-motion animation. In several scenes the TV kept getting lighter/darker. Drove my wife mad.


I've sent an email to Panasonic about the issue and have a case #, but need to follow up with a phone call. My first use of the plasma was the break-in slides, D-Nice's user settings AND service menu settings. My worry is that I've messed with the service menu. Is this going to cause a problem with the warranty?

I wouldn't bother following up on this as it can't be corrected, lessened or otherwise as it is designed to work that way using any normal controls on the tv. I have a 50G20 & am really PO'd about this feature. I have tried every setting within reason & it continues to float. I swear I see it more now than when the set was new.


This is becoming a deal breaker for me with this set & if I could afford to I would likely get rid of it. It's unfortunate as it is so good in so many other aspects but this is just a stupid design at work. I'm amazed this set gets good reviews with this occurring frequently. On bright content the set is terrific but I like dark movies sometimes too.
 
#1,189 ·

Quote:
Originally Posted by Camster /forum/post/19635472


... I swear I see it more now than when the set was new.

Same here!
One of the reasons why I decided to buy the VT25 is because of its "near pio" black level performance...



I watched quite a few movies with dark scenes since July and while there was a difference in percieved black (mainly on top/bottom black bars in 2.35:1 movies) when going from a bright scene (inky black looking bars) to a darker scene (light black looking bars) I had never experienced multiple brightness shifts in the same scene until last week.


I've been watching 4 or 5 movies this week and brightness fluctuation is now easily noticeable especially on dark scenes in widescreen (2.35:1) movies. I also watched the extended version of Avatar last night which was 16:9 (full screen) and didn't notice any brightness fluctuation but then I was not looking for it...


I'm pretty sure that my VT didn't have the brightness fluctuation issue for the first four months of use. I don't know why this problem appeared last week. At first I thought it had something to do with the settings...
 
#1,190 ·
I've started noticing the issue with my two week old 58" VT25. Fortunately it's not generally noticeable for most full screen content. When movies aren't 16:9 it's quite noticeable. It's also very noticeable on the PS3 menu screens. I'm pretty disappointed as a TV of this price shouldn't have this kind of issue. I have a couple more weeks to decide whether to return it. It'll be a tough decision as the TV is otherwise very good.
 
#1,192 ·
I fooled around with the VT settings today to see if I could reduce the fluctuation a bit. Out of curiosity I tried restoring all settings to default but it didn't do the trick, fluctuation remained in all its glory.



Tried a few other things like zooming in the picture to remove black bars from the display area and it did seem to reduce (maybe even eliminate) brightness fluctuation a lot. I was also able to lessen fluctuation by setting the screen size to 4:3 with 4:3 vertical side bar brightness set to bright. But those two options crop the movie image plus I don't really like white bars on my TV screen
. I was finally able to almost completely get rid of fluctuation with 2.35:1 movies (picture mode set to full) by using custom picture mode with the AGC option set to 15 in the pro settings menu. This is the best option for me so far. Too sad I can't change that AGC in THX mode cause I find THX picture mode a lot better than custom...


I've tried all those settings with only one movie tho...
 
#1,193 ·
Even with your VT in full screen I'm sure it's still floating. It's hard to see. The best way to see it is to pause a scene on the screen and then shine a light in front of the CATS sensor, and then move turn the light on and off. You will see it float up and down as you turn the light on and off.


Even if they kept the floating "feature" they should at least put it on a smooth gradual transition instead of a on/off type feature. It wouldn't be noticeable at all if it were gradual.


At this point, my next TV might be a direct lit LED panel with zoned dimming... or save up for a Kuro.


I think this floating feature is part of some energy star thing?
 
#1,196 ·
I have one of those USB-LED flex lights that looks like this:




Unfortunately, mine no longer works. I wonder if that can be powered by the TV USB port and then set up to shine on the sensor?


NewEgg has it for $3 (w/ $6 S&H!!), but I'm sure I could pick one up at a local Fry's store.
 
#1,197 ·

Quote:
Originally Posted by dhan /forum/post/19637513


I don't mind floating blacks that I can't or hardly can see... But when they become this obvious it's another story. CATS is turn off btw.

Ok I just realized that even with CATS set to off the VT brightness still fluctuates when turning on and off a flash light in front of the sensor.
 
#1,198 ·

Quote:
Originally Posted by dhan /forum/post/19637673


Ok I just realized that even with CATS set to off the VT brightness still fluctuates when turning on and off a flash light in front of the sensor.

Whew, just read thru this damn thread. Lot of good info here. I'm a little shocked the CATS sensor is still making adjustments when set to "OFF". The last couple of years Ive been a watch a movie in the dark kinda guy, with just a backlight. The one lamp I have (dim 65w), is off to the side and does not affect PQ during night time programming. I'm wondering if stopping watching movies in a fully dark room would help some of this issue.


The USB light above looks neat too, just seems like a PITA to deal with.
 
#1,199 ·

Quote:
Originally Posted by dhan /forum/post/19637673


Ok I just realized that even with CATS set to off the VT brightness still fluctuates when turning on and off a flash light in front of the sensor.

I'm just thinking...


What if the sensor is removed?


Not putting a tape, but actually removing it. I think the sensor is catching light from the panel itself (the panel is too bright and the inside of the TV gets too much light as so the faulty CATS sensor) and that's why the floating blacks issue no matter if it's on/off and there is no light on the room... If it works the other way (putting light) maybe it should work removing it or shielding it from any kind of light (in or out).
 
#1,200 ·

Quote:
Originally Posted by ElwayLite /forum/post/19640965


Whew, just read thru this damn thread. Lot of good info here. I'm a little shocked the CATS sensor is still making adjustments when set to "OFF". The last couple of years Ive been a watch a movie in the dark kinda guy, with just a backlight. The one lamp I have (dim 65w), is off to the side and does not affect PQ during night time programming. I'm wondering if stopping watching movies in a fully dark room would help some of this issue.


The USB light above looks neat too, just seems like a PITA to deal with.

It will still happen but will be far less noticeable.
 
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