Over the last several months complaints that Panasonic's plasma HDTVs experience sudden adverse changes in their black levels after a certain number of viewing hours have been piling up in an AVSForum thread, and now that behavior has been confirmed, though not very well explained, in a response the company sent to CNET today:
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 The new
