The Pentax 645Z supports a maximum video resolution of 1920 x 1080 pixels. That's over two times the video resolution of the most common video resolution of 1280 x 720 pixels (which is also supported by this Pentax digital camera). A video resolution of 1920 x 1080 pixels is equivalent to Full HD video. You will require a Full HD TV or better to appreciate this level of detail.
This camera's video resolution (1920 x 1080 pixels) is in fact the best supported video resolution amongst all SLR cameras that were launched around the same time as the 645Z.
Amongst similar types of camera the worst supported video resolution is 320 x 240 pixels.