Patent GB-779862-A (GB)
Title: Method of recording pictures on cinematograph film
IPC: H04N5/84
Filed: 1952-07-28
Abstract: 779,862. Television. GREENHEAD, B. R., and HIGH-DEFINITION FILMS, Ltd. July 28, 1953 [July 28, 1952], No. 19003/52. Class 40 (3). In an arrangement for the production of kinematographic films in which the scenes to be filmed are first converted into television signals which are then reproduced as images on a picture reproducing tube and recorded on kinematograph film a control signal produced independently of the television signals is also supplied to the picture tube so as to produce thereon a plurality of areas having different, predetermined, light intensities related to the light intensity requirements of the particular film employed and the " lift " and " gain " of the television signals is adjusted to make the brightness of selected parts of the reproduced television images correspond to the brightness of selected one of the plurality of areas. As shown in Fig. 1, the control signal, which comprises a step-wedge waveform is produced by a generator 11, is supplied via a gate circuit 12, " opened " either during portion of the line or of the frame blanking period, to a mixing circuit 3 in which it is combined with television signals representative of the scenes to be filmed and produced by television cameras 1, 2 and associated control units 1a and 2a. The combined signals are then supplied to a picture reproducing tube 4 the screen of which is photographed by means of an intermittent. motion kinematograph camera 5 the gate 19 of which is adjusted either to exclude or to include in the optical path that portion of the screen of tube 4 on which the light areas representative of the control signal are produced such portion being either at the top or bottom of the television picture and produced by scanning additional lines during the frame blanking period or at either side of the picture and produced by scanning an additional length of line, the recording of such light areas on the film affording a check on the subsequent processing of the film. In either case (i.e. whether the light areas are recorded on the film or not) the control signal is adjusted so that the light intensity of two of the areas correspond respectively to the minimum and maximum light intensities which are permissible for the film employed (in camera 5) and the black and peak white levels of the television signals are aligned respectively with these two values of the control signal by adjustment of the camera control units 1a, 2a, on monitor tubes in which the signal waveform of both the control signal and the television signal are displayed. With these adjustments made a check on the operation of the complete system is afforded by the readings of two meters 15, 15a which, by means of associated photo-electric cells 14, 14a, slits 16, 16a and mirror 13, indicate respectively the intensities of the two areas and also by observation of monitor tubes 6 ... 9 which produce the same display as tube 4. The control signal may be distorted to compensate for the non- linear response characteristic of tube 4 and instead of being produced by the step generator 11 may be generated by means of a television camera tube, e.g. a monoscope and may have a form other than step-wedge. In a modification of the invention the monitor cathode-ray tubes may be provided with a photometer arrangement producing a series of standard light intensities by optical means with which the light intensities produced by the control signal are compared and adjusted to obtain the desired operating and recording characteristics. Specification 779,863 is referred to.