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NEGATIVE FILM 49
(3) Positive-Type Dyed Film for Variable-Area Sound Originals
Early variable-area, 35-mm sound originals were recorded on ordinary release positive film of low resolving power (50 lines per millimeter) when double-system sound was first introduced in 1928 and 1929: When 16-mm sound was attempted using the same emulsions, the results were not satisfactory. Since survival of the 16-mm sound-recording equipment industry depended commercially upon improvement in sound reproduction, strenuous efforts were made to improve both the sound-recording machinery and the film.
Eastman 5:372 is probably the best material on the American market for variable-area 16-mm recording. The film uses a nonhalation bluedyed base of an acetate type that has low initial shrinkage, low ultimate shrinkage, and is quite accurately cut and perforated. The resolving
TABLE V
Positive Type Film for Variable Area Sound Recording
Manufacturer Code # Tradename Base resolving
Lines/mm
rated
'solvin:
power
Eastman 5372 Fine Grain Sound Ee Blue • 150
Kodak cording
Safety Type 5372
power of the emulsion is rated at 150 lines per millimeter ; values close to this can be realized in practice. The emulsion is blue-sensitive (colorblind)* and has excellent keeping qualities and shows but little change in exposure speed with age. Since it is a fine-grain emulsion, emulsion turbidity is quite low, resulting in relatively little image spread. The consistency of sensitometric characteristics from one manufacturing lot to another is quite high, indicating that the material is controlled well in manufacture. The future will no doubt see competitive materials appearing on the market as the demand for this class of film material increases. Table V lists this common film for variable-area sound originals. It is often used in recording television picture images photographed from the face of a television program monitor tube.
(4) Negative Film for Special Purposes
As wTill be pointed out later (Chapter IV), 16-mm negative raw stock is rarely used for the original material for 16-mm release prints because * "Color-blind" is a trade term meaning unscnsitized for color.