Journal of the Society of Motion Picture Engineers (1930-1949)

1949 SPLICING IN VIDEO RECORDING 249 incident light does not contribute to the formation of a particular image point, but instead is spread over a large area of the film, thus contributing nothing but a general fog. PERSISTENCE IN RELATION TO THE ELECTRONIC SHUTTER In this respect electronic and mechanical shutters behave quite differently and require individual consideration. The case of the electronic shutter, illustrated in Fig. 3 will be considered first. The top figure simply repeats the camera cycle which is shown in Fig. 1. The pulldown interval shown here is the maximum available for pulldown and is greater than the time actually required by the camera. r J f/esr Line. Fig. 3 — Timing diagram — electronic shutter. The central figure shows the actual pulldown interval of the camera. It will be noted that the end of actual pulldown has been made to coincide with the end of the available interval, this phasing being the most advantageous, as will be seen. The bottom figure shows the light-output curves of the first and last of the 525 lines of the television frame. The 523 intervening lines are not shown because of the crowding that would result. The lines just outside the exposure interval are not shown because they do not exist on the cathode-ray tube, being blanked out electronically by the timing circuits. The exposure for each line is calculated by integrating from the time of occurrence of that line to the time at which pulldown starts, indicated by the dotted line. The first line of the frame is thus integrated over a very long time and the exposure is essentially equal to