Cinematographic annual : 1931 (1931)

44 CINEMATOGRAPHIC ANNUAL length the change is so gradual that no variation in density from top to the bottom of the frame can be detected if the fade is produced by leading the film into the treating solution by a continuous instead of stepwise motion. This makes possible a wider choice of methods of timing. If the handling is to be entirely manual, then the stepwise method is probably the best choice because of the difficulty of estimating the velocity in a continuous motion. It is recommended to adjust the concentration of the solution so that the process is complete in about 10 minutes. ESCAPEMENT SQUCGGCE PROCRAM TINGING T<\PEL Fig. 7 Schematic Drawing of Machine for Making Fades with Tape foe Program Timing If the time of treatment is to vary directly as the length of film traversed, the film can be led into the bath either one frame at a time at equal time intervals or continuously by the use of any one of the common mechanical arrangements for producing motion at a constant rate. The use of mechanical timing means is very desirable even though a large part of the process is to be carried on manually. If the time of treatment is not required to increase directly as the length of film, then a more complicated timing means must be chosen. As shown in Figure 5, for the dye treatment the relationship between time of treatment and length traversed in exponential, a relationship which is not attained precisely in a simple mechanical device. If the motion is controlled by the use of a cam of special shape the apparatus is somewhat expensive and usually awkward and difficult to alter for varying treatment.