CNET did a little bit of sleuthing and convincing, and Panasonic emailed them a statement that was issued in response to the black level complaints. The statement claims that “background brightness will increase,” but says the change is “automatic” over the TVs’ lifespan and a normal operation that will “achieve the optimal picture performance throughout the life of the set.” Here is the statement CNET received via email:
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.
CNET tried to further their investigation with the electronics company, but Panasonic has yet to respond.