viewer. Examples A 625-line analog (e.g., 50 Hz PAL) television picture is divided into 576 visible lines from top to bottom. Suppose a card featuring horizontal black and white stripes is placed in front of the camera. The effective vertical resolution of the TV system is equal to the largest number of stripes that can be within the picture height and appear as individual stripes. Since it is unlikely the stripes will line up perfectly with the lines on the camera's sensor, the number is slightly less than 576. Using a Kell factor of 0.7, the number can be determined to be 0.7×576 = 403.2 lines of resolution. Kell factor can be used to determine the horizontal resolution that is required to match the vertical resolution attained by a given number of scan lines. For 576i at 50 Hz, given its 4:3 aspect ratio, the required horizontal resolution must be 4/3 times the effective vertical resolution, or (4/3)×0.7×576 = 537.6 pixels per line. Taken further, since 537.6 pixels is equal to a maximum of 268.8 cycles for an alternating pixel pattern, and given 576i 50 Hz has an active line period of 52μs, its luminance signal requires a bandwidth of 268.8/52 = 5.17 MHz. Kell factor applies equally to digital devices. Using a Kell factor of 0.9, a 1080p HDTV video system using a CCD camera and an LCD or plasma display will only have 1728×972 lines of resolution. History See also Aliasing Moiré pattern Optical resolution Resel References M. Robin, "Revisiting Kell", Broadcast Engineering, May 2003. S. Mullen, "Just What is 1080?", HDV@Work, Feb. 2006. J. Amanatides, "Antialiasing of Interlaced Video Animation", SIGGRAPH 90. G. Tonge, "The Television Scanning Process", SMPTE Journal, July 1984 pg 657 Kell factor explained in simple terms Television technology