variation in the value of the pixel, and as all the pixels don't react identically, some change more rapidly than the others and in the end the user sees video noise. Here, for example, is the situation with the ViewSonic VX924. The panel is set to transition...

a slight reddish track behind the mouse cursor when moving it laterally from left to right on a blue background. Also, a few "shear" effects like those we'd observed with the VX924 were also discernable here. But fortunately that effect has been greatly reduced...