The Brightness of Outdoor Scenes and Its Relation to Television Transmission

The average brightness of typical outdoor scenes has been determined by computation and by measurement. The average brightness of some scenes was found to be over 1000 candles per square foot, and of other scenes nearly zero. In many cases the average brightness lay between twenty and 200 candles per square foot. The sensitivity of a present-day television system using the Iconoscope has been found to be sufficient to permit the transmission of pictures with good quality when the average brightness of an average scene was greater than about fifteen candles per square foot. This sensitivity is sufficient for the transmission of parades, races, baseball games, and many other outdoor events. Football games, which last until near sunset, cannot always be satisfactory reproduced. Some of the Iconoscopes used in these tests are of added sensitivity, which has been achieved by means of a silver evaporation process, as well as by careful control of the purity of the materials.