Audio Video News

Do the black levels of Panasonic plasmas increase over time? Yes, the company says in response to reports carried on various websites.

The controversy began on the AVS Forum where a reader named Orta repeatedly measured the black level on his new set (model uncertain) and noticed it was rising. The story was picked up by c|net, culminating in a follow-up c|net report which included the Panasonic response.

Here is the response in its entirety:

Panasonic Viera plasma HDTVs deliver exceptional picture performance throughout the lifetime of these products. Various elements and material characteristics of all electronic displays change with use over time. In order to achieve the optimal picture performance throughout the life of the set, Panasonic Viera plasma HDTVs incorporate an automatic control which adjusts an internal driving voltage at predetermined intervals of operational hours.

As a result of this automatic voltage adjustment, background brightness will increase from its initial value. After several years of typical use, the internal material characteristics will stabilize and no additional automatic voltage adjustments are required. The Black Level at this stabilized point will yield excellent picture performance.

The newest Viera plasma HDTVs incorporate an improved automatic control which applies the voltage adjustments in smaller increments. This results in a more gradual change in the Black Level over time.

In other words, as the display ages, an automatic voltage adjustment kicks in. The problem in this case seems to be with the adjustment rather than the inherent qualities of plasmas themselves. Black level is actually known to be a particular strength of plasmas.

As Panasonic notes, all displays age, including cathode ray tubes, projector lamps, the CCFL backlighting in most LCD sets, etc.

Another thing worth noting is that Panasonic is extremely up front about the fact that plasmas age and has provided specific numbers for when they reach half of their original brightness. The 2008 Viera 1080p models reach that milestone at 100,000 hours, which would take 6.5 hours of use per day for 42 years.

This incident highlights a problem for reviewers as well as manufacturers. Try as we do to deliver definitive reviews, we cannot monitor every product to the end of its design life—except, of course, for products we own—so we can provide only a general prediction of what will happen. Perhaps we should pay more attention to aging related issues.

Update: A further c|net follow-up quoted Panasonic as saying, "Since the TVs work as designed, there's nothing to fix."