The optical response of a TFT-LCD has a hold-type characteristic. Therefore, the luminous intensity after scanning lines is kept almost constant. A TFT-LCD has an advantage over a CRT in that a luminous intensity does not reduce when an interlaced scan driving method is used. This paper describes the quality of interlaced motion pictures by using the parameters of optical transition width and frequency response. Those parameters are related to edge blur and dynamic contrast ratio, respectively. The degradation caused by an interlaced scan was compared with other intrinsic factors that degrade TFT-LCD picture quality. It was found that the interlaced scan driving method has a relatively little influence on the widening of edge blur, but causes a relatively large loss in dynamic contrast ratio.