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Proposed American Standard
16mm Motion Picture Projector
For Use With Monochrome Television Film
Chains Operating on Full-Storage Basis
(Fourth Draft)
PH22.91
6. Framing Device
6.1 The projector shall have a readily accessible means for positive framing of the picture when the projector is in operation. The range of the framing mechanism shall extend 0.025 inches above and below the standard position measured at the film. The framing device shall be free from creep during operation.
6.2 The method employed for framing shall not change the position of the projected image of the picture aperture by more than 1.0% of the picture width over the full framing range.
7. Picture Stability
7.1 Definition.
7.1.1 The stability of the image depends upon the ability of the projector to locate succeeding frames of film in exactly the same position relative to the picture aperture. Failure to perform this function perfectly results in either jump (vertical instability) or weave (horizontal instability) or both.
7.1.2 Jump and weave shall be measured in terms of the peak-to-peak excursions observed. In each case the result shall be stated as a percentage of picture width.
7.2 Standard.
7.2.1 Jump shall not exceed 0.2% of picture width.
7.2.2 Weave shall not exceed 0.15% of picture width.
7.3 Method of measurement.
7.3.1 Since jump and weave are mechanical characteristics of the projector and are independent of image magnification, it is recommended that both be measured with the greatest magnification that will still give a suffi
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ciently bright image for direct observation.
7.3.2 Jump and weave are usually measured by projecting a Steady Test Film which has an extra perforation in the center of the picture area. This test perforation is made in the same operation in which the sprocket holes are made and it is very precisely located with respect to the sprocket holes. Film of this type may be obtained from the Society of Motion Picture and Television Engineers.
8. Image Illumination
8.1 Intensity. There is no evidence to indicate that any particular significance should be attached either to the peak value of the illumination or to the exact shape of the light pulse as a function of time. Consequently, only the time average value of illumination intensity is standardized. However, in full-storage operation the duration of the light pulse will be approximately 5% of the period of a television field. This short duty cycle is likely to introduce large measurement errors unless certain precautions are observed. (See Paragraph 1.3.)
8.1.1 Definition. The intensity of illumination will be measured in Iconoscope Exposure Units (abbreviated IEU). The IEU is analogous to the foot-candle. Just as foot-candles are measured by a detector having a spectral sensitivity similar to that of the human eye, so are lEU's measured by a detector having a spectral sensitivity similar to that of the Type 1850-A iconoscope. For illumination from a blackbody radiator at a color temperature of 2700 K, a foot-candle
NOT APPROVED
146
August 1952 Journal of the SMPTE Vol. 59