The Cine Technician (1943 - 1945)

L28 T H E C I N K T K C II N I ( I \ N November December, l'.*4:» Edited by A. E. Jeakins TECHNICAL ABSTRACTS A Method of Testing Unsteadiness in Motion Picture Projectors. (Eon, W. Jones, S.M.P.E. Journal, June, 1945). This paper describes a simple device for measuring with reasonable accuracy the degree of unsteadiness in 35mm projector mechanisms, particularly where such mechanisms have to be tested after overhaul in the workshop, where it is not practicable bo reproduce theatre condii ions in terms (it i ture size, length of throw, etc. By the method described here the maxi:i i iid splaci ment be: any two fran ie 5i red while running a test film ins a suitable target, riie film target pattern for vertical jump consists o J a scries of horizontal black lines of eveu thickness covering the frame area and separated by clear spaces of equal thickness. This pattern is projected on to the face of a meter w hieh carries n fiat Fig. i Face of meter showing arrangement of dial and be tun beam 2" wide and IB" long ruled along its length with black lines of equal thickness and spacing to those of the film pattern at a pre-termined throw (Fig. 1). The beam can he moved about its centre through 360°. Am angle between projected and ruled gradings produces dark patches at intervals .done the beam (Fig. 2). Vertical jump in the projected imagi results in a horizontal shifting of these patches which is easily measured . 'I'h : nled beam is anted in fronl ol a M " ■ dial dividei | tares. The a ii from the c :ad off on a S! ale on the outer edge of i he dial. 10 has bi n -I to provide an ample range for all practi al ises. Beam angle Ftg. 2 The test film is run al normal speed and projected on to the dial which is adjusted to bring the horizontal division lines parallel with the film pattern. The bi am is then rotated from zero r< position at which the dark patches appearing on it shift back and forth along it a distance equal to one iii the squares on the dial — i.e.. one inch. Then the displacement between frames can be found as a decimal of an inch b\ the formula :— Frame displacement — tan 0 inches where 0 s the angle oi the beam from the horizontal. ; tteral wea\ e maj be mi asui I b-\ i him tical lines, rotating the beam to a vertical ud reading off alone another scale at the the dial. All Friction Drive for Developing Machines. W . G. C. Bosco, American Cinematographer, April, 1945) I I e Fonda Co. of Hollywood have developed a I'n t a ni drive for film processing machinery which tlie\ claim eliminates all risk of film damage and breakage. The driving power is applied directly to the out eland upper edges of the film-carrying rollers, but only applies when there is normal tension on the rilm. The driving action is achieved b\ creating a light constant drag or tension on the film all t hrough t he machine. The film-earning rollei s are unted on a shafting which is mounted ou -addles carried on springs: this permits the upper film-carrying rollers to be drawn downward and awa\ from the driving rollers when the film tension exceeds the amount determined by the spring adjustment. When sufficient -lack has been fed in to relieve the tension the springs draw the filmearn ing rollers into contact again with the dri\ rollers. This action takes place almost constantly throughout the machine. At the take-off n\d the friction roller keeps the tension constant to the rewind. When the film eaters the mad due a speed stablished which remains constant throughout veloping and drying process unless changed perator. iving rollers are direct h over the upper film earn ing rollers and all the driving mechanism o oi the tank and solutions. The film-carrying rollers in the wet end are mounted individually and in turn arc mounted on tree turning tubing and shafting. In addition, all film-carrying rollers are free to slide laterally on their shaft i hat i la With tin -\ stem there are no sprockets to pull or tear the film.