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Tests of Panasonic black level loss negative so far

A few hundred days of TV on-time in CNET's labs show no loss in black level performance so far on a pair of 2010 Panasonic plasmas.

After the equivalent of about 318 days of on-time, the black level of our Panasonic TC-P50G20 has not changed. Sarah Tew/CNET

Aside from reader requests for a review of the Samsung PNC8000--before you ask, no, I still haven't received a sample, so there's no ETA yet for the review--the most common question I get these days is some variation of "Any update on the long-term tests of Panasonic's 2010 plasmas?" At the risk of reporting a nonevent, here's what we know so far.

After about 1,650 hours of on-time logged on our TC-P50G20 review sample, and 920 on our TC-P50VT25, we have measured no loss in black level, or "minimum luminance level" (MLL) as the kids from a certain forum like to say. At the average daily rate of 5.2 hours of on-time per TV, that works out to about 318 and 177 days, respectively.

The 1,650-hour mark is somewhat significant because it's higher than the both the 1000 and 1500 hour marks after which, with Panasonic's 2009 plasmas, we measured losses. Our new results lend credence to Panasonic's claim that its 2010 plasmas would incorporate a "more gradual change in black levels over time" than the 2009 models.

That said, it's also true that the on-time for both of our samples still totals less than a year, and who's to say exactly when the MLL will increase. Panasonic's previous statements on this issue maintain that "background brightness will increase from its initial value" as part of the normal design of its plasmas. The company won't divulge exactly when those increases occur, or by how much, claiming that such information is a trade secret.

So all we really know so far is that the 2010 plasmas, based on our tests of two review samples sent to us by the company, show no black level loss after the first few hundred days of life. Unfortunately long-term testing takes, well, a long time, so we'll keep at it, and if we spot a change in MLL we'll report it here.

In the meantime, feel free to sound off in comments. Do these results increase your confidence in Panasonic plasma TVs, or plasmas in general? Are you still waiting for longer-term tests, or does this issue even register in your TV decision-making process?

Follow-up: Panasonic plasma black-level loss measured in long-term test (4/2/2010)
Tests point to extent of loss in Panasonic plasma black-level performance (3/2/2010)
Panasonic does not plan fix for reported black-level increases (2/9/2010)
Panasonic admits plasma TV black-level change but says picture quality still 'excellent' (2/4/2010)
Are Panasonic plasma TVs losing their dark black levels? (1/26/2010)