WRS MOTION PICTURE AND VIDEO LABORATORY
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Recommended Film Practices

Processing Motion Picture Film

Motion Picture  Film Processing at WRS 35mm, Super 16 and 16mm negative processing in Black and White and Color. Push Processing Computerized process and printing control. Computerized equipment standardization. WRS is recognized by Kodak for excellence in product quality, consistency and control procedures.

(Following article used with permission of Eastman KodakCo.) Important when selecting film-and too often overlooked-are the processing requirements for a given film and the printing needs for the whole production. One way to better appreciate the sophisticated technology that turns your exposed camera film into good projection film is to understand the processes and equipment in the modern film laboratory. In this section, we will describe the operations and equipment involved in processing and printing your film. Processing Equipment The modern motion picture laboratory uses the continuous processor, a machine that provides the most efficient way of handling long lengths of film. In essence, the continuous processor moves film through the appropriate sequences of developers, fixers, stop baths, washes, and dryer at a carefully controlled speed. The processor also controls solution temperature and agitation to produce optimum results for the particular kind of film being processed. Transport Design. The film follows a helical path by moving on partially or totally submerged banks of rollers through the various solutions (Figure 63). Squeegees (Figure 64) or wipers located between the different tanks remove most of the liquid from the film surface. The most common method of moving film through a processor is by friction between the rotating spools and the base side of the film. The other major method of moving film is by sprockets incorporated on the spools which engage the film perforations.   The film path through the processor's wet sections permits only the base side of the film to contact the rollers. In this way, the emulsion is protected from possible physical damage that might occur if the soft, wet emulsion came in contact with the plastic spool surfaces. However, in some processing machines, there may be emulsion-side rollers. These are usually undercut in the image area and are designed to contact only the edges or perforation area of the film. Some rollers have ridges that touch only the edges of the film; other rollers are flat and covered with "soft-touch" tires for uniform film support across the roller width that prevent scratching of the support in the image area (figure 65). Mechanical Specifications If film is to be processed satisfactorily as it moves through the machine, it must be immersed in solutions of the correct temperature for the proper length of time. In addition, processing solutions must be adequately replenished and filtered, and sufficiently agitated. These requirements are commonly called the mechanical specifications. Usually, the only valid major processing change made from the "normal" is for the purpose of force processing (for more camera speed). This involves increasing the time and/or temperature of the developer for negative, or first developer for reversal film. The time that film is immersed in a particular solution depends upon the length of the film path in each tank and the machine speed. Generally, time is fixed by the number of rollers per rack and the number of racks threaded in a tank. Temperatures on most processors are controlled automatically, often to within 0.1C but can usually be adjusted manually to accommodate any desired temperature changes. The laboratory also keeps a highly accurate thermometer available to double-check the processor temperature gauges. Process Control The degree of development in a negative-positive process or first development in a reversal process is the most important factor in determining the final image quality. Careful control is critical at this point. Development is affected by the temperatures and chemical composition of the developer (or first developer), the time of contact between the film and the solution, and the degree of agitation. The other processing steps are also affected by the same factors. When all is well with the process, the output from the continuous processor will be good pictures. While you can evaluate these pictures subjectively by simply looking at them, the most accurate evaluation is an objective measurement. Sensitometric control strip density values, when plotted in graphic form, give an operator objective information about the condition of the process. These measurements are made before, during, and after a processing run for maximum control of quality. Force (Push) Processing A camera operator may elect to shoot film at a higher exposure index (EI) than the film's rating, thus underexposing the film, to obtain usable footage under low-light conditions. The film turned into the lab for force processing is usually underexposed by a known degree. This underexposure can be compensated for in the first developer in a reversal process and the developer in a negative process in one of the following ways: Increase developer temperature. Increase film immersion time. Increase both the developer temperature and the immersion time. Based on control strip readings obtained from trials, slight time or temperature adjustments may be required to produce the desired picture results. Before force processing is used for regular production work, check out the particular film and process to see if the results meet expectations. Whether time or temperature (or both) are adjusted depends on how easily the changes from the normal mechanical specifications can be made in the processor. Processes Black-and-White Negative or Positive Processes Step What happens Developer Develops the exposed silver halide to metallic silver. Time and temperature control are especially important at this stage for optimum image quality. Stop Bath (optional) Stops the action of the developer carried over by the film, and cleans the developer from the film. Wash Cleans the developer from the film and stops developer action, but more slowly than a stop. Fixer Removes undeveloped silver halide from the emulsion. Wash Removes the fixer from the film. Dryer Dries the film for windup and subsequent projection or printing Black-and-White Reversal Processes Step What happens First Developer Develops the exposed light-sensitive silver-halide crystals to metallic silver (a negative image). Time and temperature control are critical at this stage in determining the effective film speed. Deliberate increase of time, temperature, or both is called force- processing. Wash Cleans the first developer from the film. Bleach Dissolves and removes the metallic-silver negative image produced in the first developer but does not affect the remaining silver halide. Wash Removes excess bleach from the film. Clearing Bath Removes the last of the bleach and prepares the film for the following steps. Re-exposure Renders the remaining silver-halide crystals developable. Second Developer Develops the silver halide exposed in the re-exposure step to a positive metallic-silver image. Wash Removes the second developer. Fixer Removes any undeveloped silver-halide grains. Wash Removes fixer from the film. Dryer Dries the film for windup and subsequent projection or printing. Color Negative or Positive Processes Step What happens Process Prebath* The rem-jet antihalation backing is conditioned. ECN, ECP Rem-jet Removal* The softened backing is removed from the film and flushed away. Developer Develops the exposed silver halide and reacts with the color coupling agents in the film to create dye layers along with a silver image. Time and temperature control are especially important for optimum image quality. Stop Bath Stops the action of the developer carried over by the film, and removes the developer from the film surface. Wash Removes excess stop bath. Fixer Removes undeveloped silver halide from the emulsion. Wash Removes excess fixer. Persulfate Bleach Accelerator** Prepares the film for action of persulfate bleach. Bleach (Ferricyanide, UL, or Persulfate) Converts the metallic-silver image formed by the developer into silver halide again. Wash Removes excess bleach. Sound-track Developer Converts the silver halide sound-track area into metallic-silver. ECP only Wash Removes excess sound-track developer. Fixer Removes silver halide formed in the bleach from the emulsion. ECN, ECP Wash Removes fixer from the film. Final Rinse Anti-bacterial rinse and wetting agent. Prepares film for drying. Dryer Dries the film for windup and subsequent projection or printing. * The prebath and rem-jet removal steps may be omitted for the positive process.**For this step, use only with persulfate bleach. Color Reversal Processes Step What happens First Developer Reduces exposed silver-halide grains in all three light-sensitive layers. The negative silver image is formed at the exposed silver-halide site. First Stop Stops the development of silver-halide grains and reduces emulsion swelling during the next wash. Wash Removes excess acid stop. Color Developer A reversal (fogging) agent makes the remaining silver halide developable without being exposed to light. The developing agent then produces a positive silver image in each layer, and the oxidized developing agent reacts with the incorporated color couplers to produce color images simultaneously at all development sites in each layer. Second Stop Stops action of the color developer. Wash Removes excess acid stop. *Persulfate Bleach Accelerator Prepares the positive silver image for bleaching. Ferricyanide Bleach Converts the metallic silver from the positive image into silver halide salts. * Persulfate Bleach Converts the metallic silver from the positive image into silver halide salts. Fixer Converts the insoluble silver halide salts into soluble complex silver thiosulfate compounds that are removed in the fixer and following wash. Wash Removes hypo and residual silver thiosulfate complex compounds that were not removed from the film in the first fixer. Stabilizer Hardens the emulsion, stabilizes the dye images and prevents water spots. Dryer Dries film for subsequent handling. * Preferred Alternate Persulfate Bleach Sequence (P-2).