NAEB Engineering Newsletter (Dec 1955)

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- 8 - CLASSIFYING 16MM. "EMULSION POSITIONS" AND "FILM WINDS " By Berten A. Holmberg Chief Engineer Radio Station KUOM General One of the more vital abilities which a person who handles 16mm. motion picture film should have is that of being adept in classifying film stock according to its " wind " and its "emulsion position." Often this must be done in a minimum of time and under lighting conditions which are far from optimum. Since a mistake can waste much valu¬ able film, it is well to commit a few simple rules to memory. After a discussion of these rules and corresponding definitions, there will be pre¬ sented herewith a proposal for simplifying certain terminology and practices related to 16mm. film production. Raw Stocks—"A Wind and B Wind " The first of these terms, " wind " refers to the manner in which single perforated 16mm. raw stock is wound onto cores as supplied by the film manufacturer. While raw film is always supplied with its emulsion wound toward the center of the core, there still remains the alternative of spooling it in such a manner that the row of sprocket perforations is either on the near or the far edge of the roll when it is placed into position in a camera or printer. A little experimentation with a few feet of single perforated film will show that the position of the perforations is determined by one*s choice of the film end that is attached to the center of the core when commencing winding. This assumes, of course, that one winds the film with the emulsion toward the center of the core as is standard practice for raw stock. In order to allow for differences in design and manufacture of various film handling devices which may call for one or the other sprocket position, it is customary for manufacturers of film to supply 16mm. single perforated stock in either of two " winds " which they designate as " A Wind" and " B Wind ." These can be quite easily distihguished from each other by inspection and the application of a simple rule. After verifying the fact that the emulsion is on the side of the film toward the core, it is merely necessary to hold up the roll of stock in such a position that the outer tail of the film hangs down from the right edge of roll. When held in this position "A Wind" stock has the sprocket perforations on the edge nearest the observer, while "B Wind" stock has the perforations on the edge away from the ob¬ server. Obviously it is possible to develop a similar rule based on having the tail of film hanging down from the left edge of the roll. Whatever the case may be, it is best that one or the other rule be used consistently so as not to become confused. Actually, film which is supplied as one type of "wind" can be converted to the other type by the simple operation of rewinding it onto another hub with the emulsion fac¬ ing the axis.