ISO 69:1998 pdf download – Cinematography — 16 mm motion-picture and magnetic-film — Cutting and perforating dimensions
A.1 Uniformity of perforating The uniformity of pitch, hole size and margin (dimensions B or B¢, C and D, and E) are important variables affecting image steadiness. Variations in these dimensions within a roll, from one perforation to the next, are more significant than variations from roll to roll. Actually, it is the maximum variation from one perforation to the next within any small group of consecutive perforations that is the most important variable. A.2 Dimensional stability The user is reminded that film dimensions can change due to moisture, temperature, and strain effect, or, in some film-base materials, due to solvent or plasticizer loss. These changes are generally uniform throughout the roll. A.3 Definition of low-shrinkage film Low-shrinkage film is film which shrinks no more than 0,2 % from its original dimensions at the time of cutting and perforating, after the film has been a) kept in the manufacturer’s normal commercial packing for six months at recommended storage conditions; b) exposed; c) processed and dried as recommended by the manufacturer; d) stored in roll form, exposed to air, for a period not to exceed 30 d at 1 8 °C to 24 °C and 50 % to 60 % relative humidity. The film is measured under the same conditions of temperature and humidity as defined in 3.1 . A.4 Choice of longitudinal pitch The choice of different pitch (B: long pitch and B¢: short pitch), for original and print motion-picture films, depends on the necessity of printing and the type of printer used. In the most common type of printer, the original and print films move continuously over a printing sprocket. Consequently, the original film must be shorter in pitch than the print film in the approximate proportion of the thickness of the film to the radius of curvature of the printing sprocket. With current printing sprocket designs, the value for this pitch differential is 0,3 %, with experience showing that a tolerance of ± 0,1 % is acceptable.