Originally Posted by feds27
Has any noticed any brightness shifting while watching Law and Order on HD TNT? I'm trying ti determine if it's a source, cablebox or my Panny causing the problem. I've also noticed it while watching MotoGP racing on Speed in standard def too. What I mean by brightness shift is while watching a scene, usually a dim courtroom scene, the brightness all of a sudden bumps up slightly and holds. I not longer have my CRT tv so I can't check if it's my cable box. I have DVR functions and when I rewind and play the same scene, the brightness shift repeats.
This is often referred to as floating blacks. Panasonic consumer models have done this to some extent for a while. Last year's models were more susceptible that the PZ8x models, but the PZ8x models can do it. The black level of the PDP actually changes in response to the APL (average picture level).
You can minimize floating blacks by reducing the Contrast setting, but I've never found anything that eliminates it completely.
This is another good reason to not mess around with cuts & gains in the service menu since there are settings that can be made there that seem to make the PDP more susceptible to floating blacks.
You can see the floating blacks pretty easily if you have a test disc that has 10%, 20%, 30%, etc window patterns. Display a darker pattern, then go to the next brighter step, wait 5 seconds or so. If the black level does not change switch the pattern to the next brightest step. At some point, you will very likely see the black surrounding the window pattern jump up in level significantly. If you have Contrast set low enough (but you don't want to go too low on these PDPs because the RGB tracking gets lumpier if you do), you should be able to display all the window patterns up to 100% without the black level jumping up. Obviously, a full field pattern won't reveal the issue because the whole screen will be filled.