Are Panasonic plasma TVs losing their dark black levels?

Users of Panasonic plasmas are reporting lighter black levels after extended periods of use.

A thread on enthusiast web site AVS forum tells of Panasonic plasmas getting grayer with age. Sarah Tew/CNET

Update March 3, 2010: CNET testing points to the extent of the black level increase in affected plasmas. Click here for details.

As CNET's HDTV reviewer, I've spent a lot of time evaluating black-level performance--that critical capability of a display to produce as dark a shade of black as possible. My testing is primarily done in a completely dark room using high-quality Blu-ray material on TVs that have been calibrated to produce a level playing field for side-by-side comparison. Those TVs are reviewed in their first hundred or so hours of life; however, my process does not consider longer-term performance.

The fact that I don't test for long-term issues, as well as the importance of black level performance, were two big reasons I took note when I received a barrage of e-mails recently, all pointing to the same content on AVS forum, an enthusiast Web site.

The forum thread, titled "G10 black levels have seemingly doubled over night," describes the level of black on the poster's Panasonic TC-PG10 series plasma precipitously becoming lighter and impairing picture quality, for no obvious reason, after a certain period of use ("doubled" in this case isn't a good thing).

Other responders to the original post have reported similar problems, many with accompanying photographic evidence. Forum posters have reported problems with other 2009 ("12G") and even 2008 ("11G") models of Panasonic plasma TVs as well.

In the forum, the TV owners describe their calls to Panasonic to complain about the issue, conversations with company representatives who, in many cases, appear to be aware of the problem, and service visits from Panasonic technicians to the homes of owners. However, as of today, no real resolution has been reported.

In one example dated January 25, an owner posted the following e-mail said to be sent from Panasonic in reply to a complaint:

"Please be advised that Panasonic is aware of the postings on AV Science (AVS) Forum whereby customers have reported the TV's black level appears to have become greyer and/or the measurements have changed from their original measurements. Our factory and QA Group will investigating these reports, and once we have additional information from them we will advise you via return e-mail.
Thank you.

Sincerely,

Viera Concierge Support Team

Panasonic Canada Inc."

I first contacted Panasonic seeking comment on January 11, and there's still no word from the company despite my repeated inquiries since then. The latest information that I've been given is that the company's U.S. public relations team was still awaiting a response from its headquarters in Japan. Panasonic does not have a good track record when it comes to responding to my requests for information in a timely manner, so it's anyone's guess when they'll reply with anything substantial.

Unfortunately, I currently don't have anything more substantial than the thread itself. One of its most damning claims comes from a well-respected calibrator who goes by the screen name D-Nice, who posted information he had received from sources inside Panasonic. In one post he wrote: "They are still good displays...they just have some issues...What really needs to happen is for 12G Panasonic owners to contact Panasonic and demand they correct [the issue]."

When I followed up with D-Nice he replied via email: "It seems as if Panasonic Engineering goofed on a portion of their software that modifies the pixel voltage levels periodically. All plasmas have a voltage control system that adjusts pixel voltage at predefined hours of use to ensure pixels do not misfire. However, Panasonic's software seems to be going overboard in this area. The end result is an elevated idle black that worsens as more hours are clocked on the display."

I haven't seen the lightening phenomenon myself, and even if I did, it would be difficult to prove whether the problem was systematic, and what caused it exactly. It's also worth noting that all posts to AVS forum can be anonymous and might include erroneous information, although the preponderance of evidence in this thread, and the many eyewitnesses, leads me to believe the problem is real.

I'll provide an update if the issue develops further, but until then, I can't provide any definitive buying advice one way or the other--our product reviews and recommendations are based on direct, hands-on experience only. However, a note linking to this post will appear on reviews of all 2009 Panasonic plasmas.

In the meantime, what do you think? Are you perfectly happy with your Panasonic plasma or have you experienced a sudden rise in black levels? If hearing about issues like this gives you pause when shopping for a new TV, what should Panasonic or any company do to restore your confidence? Let us know with a comment.

Update 1-27-2009: Included new comment and modified post quote from D-Nice; clarified date of first contact with Panasonic on this issue.

Update 2-2-2009: Updated 2009 Panasonic plasma reviews with a note and link to this article (example); began long-term test of two Panasonic models in-house (details); still no comment from Panasonic.

 

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