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The Snake Track
This particular test-film is designed to show whether or not the scanning-beam is of even intensity. The sound-signal, which produces a constant even note, is printed in a narrow strip along one-third of the sound-track area. This narrow strip weaves from side to side of the sound-track area along the full length of the film.
When projected, any unevenness of illumination would be at once noticeable by an alternating drop in volume, whilst an even note from the loudspeaker would indicate that the scanningbeam was of even brightness across the sound-track.
Sound and Picture Test-Films
Providing the projectionist with an opportunity of making a large number of tests, these films contain half-a-dozen or more excerpts from well-known feature films, plus sections of speech, piano-music and a number of other sounds, the whole covering a very wide range of different types of sound and picture. Both variable-area and variable-density recording may be in the same test-film.
Test-films have now been standardised and readers requiring the complete descriptive standard may send for British Standard No. 1488 of 1949, Test-films for 16-mm. Cinematograph Projectors (2/-) from the British Standards Institution, 24/28, Victoria-street, London, S.W.i.
Repairing Damaged Films
If two or more consecutive perforations are torn, the smallest possible section should be cut out and a careful splice made. It is not usually necessary to cut and make a join in the case of a single perforation being torn unless the film is to be used on a projector fitted with a single claw. Badly torn sections of film should, as a rule, always be removed from the film before it is used, but this does not apply to single blistered frames or other minor forms of damage, unless the particular type of damage is likely to cause a stoppage during projection.
If a damaged film will pass safely through the projector, then there is no need to cut the film and make a join. And that can be your guiding rule.
Interpunching of the film, which is probably the worst form
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