Smearing is an effect which appears in the form of 'tails' at motion pictures. This effect arises mostly in passive LCDs (STN, DSTN) due to the low action of the Liquid Crystals. When using fast motion pictures with high contrast differences, it is possible that the Liquid Crystals cannot accept the new conditions in a sufficiently quick manner. Similar effects can only be noticed at a low rate in TFT-Displays and CRT-Monitors (CRTs are always looking for a compromise in the phosphors used, i. e. between a fast reaction time and the suppression of flicker by sufficient persistence of the phosphors.)
The test patterns represent an extreme situation for a display, a fast motion picture with high contrast on a black background. First the display must make a fast change from 0 to 100% contrast, and then from 100 to 0% contrast.