The human eye and the equipment chain (2/4) If an A4 picture is viewed from more distance than 25 cm the visible resolution will proportionally diminish as the 1 arc minute of the human eye is constant. Viewing an A4 from 25 cm viewing distance isn't comfortable. A natural viewing distance might be 2 times the picture height which leads to 42 cm. This would ask only for a 178 dpi resolution with 2080x1470 dots with totally about 3Mpixels what is what the human eye can see on a 2 times picture height distance. A Typical 2 times height viewing distance applies for computer screens. The today HD resolution (1920x1080) is with 2MPixels below what a human eye could see. For TV’s or slide projection a 3 times height viewing distance is a minimum. This would only ask for a resolution of 1.7 MPixels what is already below the "Full HD" performance and a little more than the "HD ready" format. To take full advantage of the "Full HD" resolution a closer distance of 2.5 of the height is necessary. This is quite close to watch moving full frame pictures on a TV screen. The viewing distance will be even more an issue with the newly introduced Ultra HD (UHD) format with 3840x2160 pixel (8Mpixels). The viewing distance for maximum resolution is only 1.25 of the height which means 100cm for the 65" (143cmx80cm) TV screen.