Panasonic Plasma 11G / 12G Panels and Rising Black Levels

Discussion in 'Displays' started by Mike Gov, Feb 4, 2010.

  1. Mike Gov

    Mike Gov Stunt Coordinator

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    I have began reading about problems that people have reportedly developed with the Panasonic 11G/12G panels. The problem is that on these panels the black levels are rising after a certain amount of hours on the sets. Below is something I copied and pasted, it is some Panasonic patent information which is reportedly a voltage increase that is to blame for the gradual rise in black levels with these panels. There is a growing active thread on it over at AVS right now. People are saying that they noticed it and confirmed their suspicion by actually measuring the rise. http://www.avsforum.com/avs-vb/showthread.php?t=1167339

    Next, the relationship between the power-on accumulated time and initializing voltage Vr is described. FIG. 13 is a pattern diagram showing the relationship between the power-on accumulated time and discharge start voltage of panel 10 of exemplary embodiment 2 of the present invention. As the power-on accumulated time of panel 10 increases, the discharge start voltage gradually increases . The discharge characteristics vary over time, so that the following problems occur. When initializing voltage Vr is set with reference to the discharge start voltage of panel 10 having a short power-on accumulated time, extending the power-on accumulated time increases the discharge start voltage. At this time, initializing voltage Vr becomes relatively low with respect to the discharge start voltage, hence the initializing discharge becomes weak, and sufficient wall voltage cannot be generated or the priming runs short. Thus, the initializing discharge can be insufficient. While, when initializing voltage Vr is previously set to be high in expectation of the variation over time of the discharge characteristics, initializing discharge becomes stronger than necessary in panel 10 having a short power-on accumulated time, light emission that is not related to the image display becomes strong, the black luminance increases, and the contrast can degrade.

    However, the panel of the present embodiment has accumulated time measuring circuit 83, measures the power-on accumulated time, and performs control so that initializing voltage Vr increases with extension in power-on accumulated time. An image with sharp contrast can be displayed without un-stabilizing the initializing discharge regardless of the power-on accumulated time from the initial stage of the manufacturing of plasma display device 1.

    An example of the method of controlling initializing voltage Vr based on the power-on accumulated time is a method of continuously increasing initializing voltage Vr with extension in power-on accumulated time. In the present embodiment, a plurality of accumulated time thresholds are set, the power-on accumulated time supplied from accumulated time measuring circuit 83 is compared with the accumulated time thresholds, and initializing voltage Vr is increased whenever the power-on accumulated time exceeds the accumulated time thresholds. FIG. 14A and FIG. 14B show a control method of the initializing voltage and a transition of the contrast ratio in accordance with exemplary embodiment 2. FIG. 14A shows the relationship between the power-on accumulated time and initializing voltage Vr, and FIG. 14B shows the relationship between the power-on accumulated time and the contrast ratio. In exemplary embodiment 2, three accumulated time thresholds of 650 hours, 850 hours, and 1000 hours are set, and initializing voltage Vr is increased by 5 (V) when the power-on accumulated time exceeds 650 hours. The increase in initializing voltage is performed not only in normal-temperature driving mode but also in low-temperature driving mode and high-temperature driving mode, and regardless of the APL value. When the power-on accumulated time exceeds 850 hours, initializing voltage Vr is further increased by 5 (V). When the power-on accumulated time exceeds 1000 hours, initializing voltage Vr is further increased by 5 (V).

    In the present embodiment, as the discharge start voltage is increased in response to extension in power-on accumulated time, initializing voltage Vr is increased. Therefore, image display with a contrast stabilized at a high level is allowed regardless of the power-on accumulated time.


    It is considered that the panel is hardly affected by increase over time in discharge start voltage when initializing voltage Vr is high, so that increase rate of the initializing voltage may be decreased as initializing voltage Vr becomes high.
     
  2. Mike Gov

    Mike Gov Stunt Coordinator

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  3. Gregg Loewen

    Gregg Loewen Video Standards Instructor, THX Ltd.
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    yup
    Stay tuned...
    Ill post info as I hear about it.
     
  4. douglas-b

    douglas-b Stunt Coordinator

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    Wow, I somehow misssed the reply from Panasonic over this. It was the main reason I did not upgrade my set this year.
     
  5. Mike Gov

    Mike Gov Stunt Coordinator

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    Well it appears that Panasonic has agreed that they designed their plasma displays to increase idle black over time. They are changing the design a bit for the 2010 models saying it will "improve" this premature idle black issue.
    Fortunately my display still looks good, but I am not appreciative of Panasonic stance on this issue since they appear to be saying the display was designed this way even though some displays may have a large jump in MLL in a relative short period of time.
    I have to believe from what I have read that some displays are developing this problem because of this design and feel that Panasonic should take some action in those cases. It appears that they will not be.
    Here is the latest CNET reponse.
    Any input here would be greatly appreciated, thanks.


    http://news.cnet.com/8301-17938_105-10449939-1.html?tag=mncol
     
  6. Mike Gov

    Mike Gov Stunt Coordinator

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  7. Patsfan35

    Patsfan35 Auditioning

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    Well I hope my long exhausted research on what TV to buy does not come back to bite me in the you know what. I just bought the Panasonic TCP42G10 3 weeks ago now. I hope I dont see black levels rise anytime soon.
     
  8. Nascar-Dog

    Nascar-Dog Auditioning

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    I gave up on Panasonic and ordered a Pioneer PRO-101FD.
    Can't wait for it to arrive this week.
     
  9. Charles Smith

    Charles Smith Extremely Talented Member
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    I've been looking at plasma TVs over the past few days, figuring I'll end up with a Panasonic because they seem to win the general consensus for best overall picture quality -- barring, perhaps, the Pioneers which are now out of the picture (and out of my budget). Today I was googling and found the above-mentioned CNET report on this black level issue that surfaced in February 2010, and which was responded to somewhat lamely by Panasonic. Does anyone here know of any follow-up since March or April 2010? I haven't found anything yet.

     

    It just happens that good black level has been a thing with me for years. I'm not a techie or a pro, just someone who was taught early on to pay attention to picture quality. Coming across this bit of news was quite the shock, but I'm glad I discovered it now rather than later

     

    The next obvious question is what other brands and models -- in the serious opinions of people here -- are equally worth considering? This will be a 1080p, 46" or 50" based on viewing area and seating distance, in a room where I don't have to please anyone but myself on any point whatever. Reflections won't be an issue because the windows darken well and I'm free to determine what lighting goes where. Most of this TV's use will be devoted to watching my BLU/DVD/LD collection, plus a little cable TV. No gaming, no computers, nothing else at all -- except maybe the occasional card inserted to view photos or video. My only concern about burn-in would be from letterboxing and pillarboxing, but I can say I've been watching correct aspect ratios on an old CRT for a couple of decades without any sign of burn-in.

     

    Let me know if more info is needed, and thanks in advance for any guidance.

     
     
  10. elwaylite

    elwaylite Stunt Coordinator

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    HT Mag and Cnet have held on to their 2010 test models for extended periods and have no rise in black (one has 1500 hours). The rise is still their, but it's over a much longer time, and is more gradual. I'd not sweat it, the Panny's are nice plasmas.
     
  11. Charles Smith

    Charles Smith Extremely Talented Member
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    Thank you. It looks like I'll be pulling the trigger on the 50" G20.
     
  12. questrider

    questrider Second Unit
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    cnet's review for the TC-P50G20 has been updated as of October 19, 2010:


    http://reviews.cnet.com/flat-panel-tvs/panasonic-viera-tc-p50g20/4505-6482_7-33957042.html


    Editors' note, October 19, 2010: The Features rating on this review has been reduced from "8" to "7" to align more properly with other available products, including the new GT25 series. As a result the Overall rating fell from 7.7 to 7.4. Also, after about 2,400 hours the black level performance of our TC-P50GT20 [must be a misprint since cnet was testing the TC-P50G20/VT25] review sample has risen, but not enough to affect the overall performance score. According to Panasonic it should not increase much further.



    And here's the article from the referenced "According to Panasonic" link from October 7, 2010:


    2010 Panasonic plasma TVs: still lose black levels, but should remain 'blacker' than competition

    http://news.cnet.com/8301-17938_105-20018722-1.html
     

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