Patent GB-765460-A (GB)
Title: Improvements in or relating to photographic colour film contact printer
IPC: G03B27/72
Filed: 1953-09-24
Abstract: 765,460. Photographic contact printing apparatus. WARNER BROS. PICTURES, Inc. Sept. 24, 1953 [Nov. 7, 1952], No. 26318/53. Classes 97(1) and 98(2) A colour kinematograph film contact printer comprises means for bringing into contact a processed negative colour film and an unexposed light - sensitive positive film and for exposing them to light from a variable aperture illuminated by way of an optical system from a light source of controllable intensity, and holders bearing adjacent transparent and filter portions arranged so that when a filter portion is removed from the light path the adjacent transparent portion is moved into the light path under the control of switchcontrolled electric circuits. A third protective film may be sandwiched between the positive film. As shown, a picture- and sound trackbearing negative colour film 32 and an unexposed positive film 33 are forwarded from supply reels by a sprocket 50 (not shown), and then pass separately to the printing gate 57 where a transparent film 31 which may carry sub-titles is fed between the negative and the rear gate guide to protect the negative from abra- 'sion, the three films then being fed in loops of different sizes to a draw-off sprocket 61 (not shown) and thence to take-up reels. Printing light at the gate aperture 30 is provided by a lamp 19 through a heat filter 17, condenser 21, adjustable filter assembly 23, relay lens 24, positive emulsion colour balance correction filter pack 25, prism 26, adjustable aperture 27, and a cylindrical concentrating lens 28. The lamp is cooled by an upward forced draught and its brightness is held steady by means of a rheostat adjusted to bring to a standard value the reading of a meter 68 operated by a photocell excited by the lamp through a heat filter 70, adjustable tapered absorbing wedge 71 and an ultra-violet cell-protecting filter 73, a manually operable sliding shutter 76 blanking off the light except when a reading is required. To enable the lamp to be focused, its socket is carried by a platform 150 adjustable by a screw 149 while a tube 67 carrying the cell shutter and filters is axially movable towards the meter to facilitate replacement of the lamp. The filter assembly 23 comprises yellow, cyan, and magenta sets each of five filters of densities related by a geometrical progression of ratio two, each filter disc 131 typically of gelatin together with an adjacent clear disc 132 being carried in a holder by screws fitting tightly in one securing hole in the discs and loosely in the other securing holes, each holder 127 being rotatable clockwise from the rest position shown upon energization of a solenoid 114. resilient pads 136, 137 arresting the holder in its extreme positions. One negative film margin is notched at the beginning of every sequence requiring a change in printing light to operate micro-switches 52, 53 which actuate respectively a solenoid 90 (not shown) adjusting the movable plate 36 limiting the aperture 27 through a linkage set manually after each change in accordance with a cue sheet prepared beforehand and moving down one step an indicator thereon, and a solenoid 100 (Fig. 12, not shown) which causes a bar 99 to drop one step on a board 92 having a common live bar 102 and sets 93, 94, 95 of five bars for yellow, cyan and magenta respectively in which pins 97 are placed in accordance-with the estimated filter requirements for producing a satisfactory print. For rapid movement of the filters, each solenoid is initially energized through parallel coils, one of which cuts out the other by opening a switch such as 121 to reduce the solenoid field to a holding value. If the switch does not open, a circuit through it and a resistor operates a buzzer which is so connected that it may be switched off by a manually operated solenpid only 'when the fault is traced. A test circuit for the buzzer is provided, as is a manually operable switch for breaking the circuit .from film-operated switches without shutting down the whole printer. U.S.A. Specification 1,863,051 is referred to.