GB845154A - Method of adjusting an electronic film previewer - Google Patents

Abstract

845,154. Focal viewing. HAZLETINE CORPORATION. June 2, 1958 [June 21, 1957], No. 17529/58. Class 40(3). The calibration of control devices 22, 23, 24 in the red, green and blue channels respectively of an electronic previewer in which signals representative of the latter colour components of a transparency 10 scanned by a flying-spot scanning tube 14 and co-operating optical and photoelectric devices 16 - 20 are supplied, in a processing circuit 21 which simulates the effects of conventional photographic printing techniques (e.g. spectral overlap and gamma characteristics), to a picture reproducing tube 12, is adjusted by visually comparing the image 13 reproduced by tube 12 with an optically projected image 32 of a positive transparency 31 produced by conventional photographic techniques from the transparency 10 (as depicted in the block 34) and then adjusting the resistances 25, 26, 27 until the image 13 is similar to image 32, the control devices 22, 23, 24 being previously set at a reference position corresponding to the densities of the filters 37 R; G; B; employed in the photographic process. Since the control devices 22, 23, 24 are calibrated in terms of the densities of the filters employed in photographic processes the latter requirements may be read directly from the settings required to produce an acceptable image 13 when any transparency is employed in the position 10. A similar adjustment technique may be employed when it is required to adjust the operation of the processing circuit 21. Specification 841,125 is referred to.