A television system must be designed, therefore, to embrace the essential capabilities of these senses, particularly the sense of .
The aspects of vision that must be considered include the ability of the human eye to distinguish the brightness, colours, details, sizes, shapes, and positions of objects in a scene before it.
The first requirement to be met in image analysis is that the reproduced picture shall not flicker, since flicker induces severe visual fatigue.
A television system involves equipment located at the source of production, equipment located in the home of the viewer, and equipment used to convey the television signal from the producer to the viewer.
The purpose of all of this equipment, as stated in the introduction to this article, is to extend the human senses of vision and hearing beyond their natural limits of physical distance.
At the receiver the waves are translated back into a corresponding sequence of lights and shadows, and these are reassembled in their correct positions on the viewing screen.; that is, the brain retains the impression of illumination for about one-tenth of a second after the source of light is removed from the eye.
If, therefore, the process of image synthesis takes less than one-tenth of a second, the eye will be unaware that the picture is being reassembled piecemeal, and it will appear as if the whole surface of the viewing screen is continuously illuminated.