PDP cells are just tiny fluorescent bulbs and just like fluorescent bulbs they have a very difficult time turning on when they have been off for any length of time. To make sure the cell can be turned off and on at high speeds in a predictable manner the cell must be primed (flooded with free electrons). To create these priming electrons every cell (all at once) undergoes a weak discharge to create priming particles once every frame. Unfortunately unwanted light is emitted which we see as black level. This all-cell discharge occurs in a step referred to as Reset or Initialization or Setup.
- the Reset/Initialization step also serves the purpose of setting all pixels into a uniform low level wall charge state so that subsequent addressing of pixels properly occurs. Without a reset step it is very difficult to control the pixels on and off states. This is where the terms "reset" or "Initialize" or "Setup" come from. The pixels are set in a proper state heading into the addressing period. However, this is confusing so let us just stick to the reset vs black level problem.]
To eliminate black level completely in a PDP the all-cell reset (aka – initialization/setup) step in the driving waveform must either be eliminated completely or produce no visible light emission to the viewer.
However, without priming, the individual cells have a high probability of not discharging (misfiring). If many cells misfire then at the very least the picture will be full of black specs (called 'black noise').
Research is focusing on finding a way to generate and maintain priming without requiring any all-cell initializations or by hiding the light emitted from the all-cell initialization.
Below is a graphic that I made attempting to describe the difference between the various driving methods and how they relate to black level. The red bars represent the all-cell initialization
periods each frame that generate black level. The goal is to reduce and eventually eliminate them (as in the ECC case). Note that I have normalized the number of subfields to 8 here to make things a little easier to understand. In reality Pioneer uses 14 subfields and Panasonic uses 10 (used 8 before 600Hz).