Radio age research, manufacturing, communications, broadcasting, television (1941)

Television, Films and the Human Eye RESEARCH REVEALS THAT THE TELEVISION IMAGE ORTHICON TUBE AND THE EYE ARE EQUALLY SENSITIVE. FAR SURPASSING FASTEST PHOTOGRAPHIC FILM IN RESPONSE TO LIGHT By Dr. Albert Rose RCA Laboratories, Princeton, N. J. A MOVIE patron steps from the bright outdoors into the dim interior of a theater. Some mo- ments elapse before his eyes be- come sufficiently adapted to the dark to guide him to a seat. The seat he chooses is circumscribed— within limits. He cannot, for ex- ample, approach within arm's length of the screen with the in- tent of determining whether the heroine wears 60- or 80-mesh sheer hose, for by design the seats stop thirty or more feet short of the screen. The viewer of a home television receiver is not subject to the same limitations. The aim, at least, is that he may view his picture with enough light in the room to see comfortably. There is, moreover, no barrier to prevent him from tak- ing his seat where he can exhaust THESE FOUR PHOTOGRAPHS SHOW THE INCREASED EFFICIENCY OF THE IMAGE ORTHICON OVER THE MOST SENSITIVE FILM UNDER NORMAL AND LOW LIGHTING CONDITIONS. PICTURE ON LEFT SIDE OF EACH FILM SQUARE SHOWS THE IMAGE AS PICKED UP BY IMAGE ORTHICON AND PHOTOGRAPHED DIRECT FROM KINESCOPE. PICTURE ON RIGHT OF EACH SQUARE IS THE IMAGE AS RECORDED BY CAMERA. ONLY WHEN LIGHT WAS MAXIMUM WAS FILM ABLE TO RECORD AN IMAGE AL- THOUGH IMAGE ORTHICON TUBE WAS SUCCESSFUL WHEN ILLUMINATION WAS REDUCED 99 PERCENT. FIGURES UNDER EACH SQUARE INDICATE RELATIVE INTEN- SITY OF LIGHT. the last particle of picture detail. Both these considerations, i.e., picture brightness and viewing dis- tance, determine the technical standards that a picture must meet in order to be judged satisfactory by the eye. Both are more severe for a television picture than for a motion picture. Because the judgment of picture quality is made by the eye, it is highly desirable to be able to spe- cify the performance of the eye quantitatively and in such terms or units as will allow ready compari- son with the performance of mo- tion picture film or a television system. The problem of choosing a per- formance scale that can be applied with equal validity to motion pic- ture film, the eye and television pick-up tubes is considerably sim- plified by the fact that all three devices are subject ultimately to the same limitations. These limita- tions are set by the statistical fluc- tuations in the absorption of light. The fluctuations can give rise to graininess in films, to "noise" in a television picture and to limited half-tone discrimination in the eye. They also permit a unified approach to performance evaluations — an approach whose technical economy can readily be appreciated since only a single number, correspond- ing to the light efficiency, is needed to specify the performance range of a well designed picture pick-up device. And this statement holds equally for the eye, photographic film and pick-up tubes. Here, in brief, are a few of the conclusions to which the above uni- fied approach leads. More Sensitive Than Film The sensitivity of the image orthicon and the human eye are approximately equal and each is about ten times as sensitive as photographic film. The comparison pictures in the accompanying photo- graph, when properly interpreted, support the factor of ten betweeen 0.07 0.02 [28 RADIO AGEl