Don Larsson writes: >A correspondent off this list posed a question that the more >technologically-inclined here might be able to answer: exactly (or >approximately) how much time of each 1/24th of a second during normal >sound projection is "dark"? This depends on the size of the shutter blades and the time taken by the intermittent mechanism to advance the film. Both vary between projector designs. The smaller the shutter and/or quicker the movement, the more light-efficient your xenon lamp is (i.e. you get more foot-lamberts per watt of light), but the more critical your shutter timing is. Larger blades and/or smaller movements make shutter timing easier but are less light-efficient. A small blade and/or quick movement are highly desirable if showing silents, because they will tolerate a lower speed before a flicker becomes visible. The most efficient projector design I know of in this regard is the Philips/Kinoton FP20, which will happily go down to 18fps without a significant flicker and without fitting a special shutter. However, the tiny margins for error this system creates work only because there are no belts in the mechanism and the shutter is single-blade, double-geared (i.e. it goes through two complete rotations for every pulldown). Belt-driven machines such as the Cinemecannica Victoria 5 have larger blades and thus a longer 'dark time', but this is needed because the variance in transmission as the belt wares through its lifetime would eventually cause ghosting if the blades were any smaller. Leo Dr. Leo Enticknap Director, Northern Region Film and Television Archive School of Arts and Media University of Teesside Middlesbrough TS1 3BA United Kingdom Tel. +44-(0)1642 384022 Fax. +44-(0)1642 384099 Brainfryer: +44-(0)7710 417383 ---- Online resources for film/TV studies may be found at ScreenSite http://www.tcf.ua.edu/ScreenSite