Sequential Contrast / Simultaneous Contrast
There are several ways of measuring contrast ratios.
Sequential contrast consists in measuring the luminance ratio between a full white picture and a full black picture sequentially. Values are generally high.
Simultaneous contrast consists in measuring the luminance ratio between various areas of a given pattern. Usually a black and white checker-board pattern is used.
As, for optical reasons, two colors, side by side, interacts with each other (crosstalk), the value is generally lower than the sequential contrast but more representative of the quality of the display.