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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
meter and an IEU meter will give identical readings. (See Paragraph 1.3.)
8.1.2 Standard. The intensity of illumination shall be at least lEU'S.* (See Paragraph 1 .3.)
8.1.3 Method of measurement.
8.1.3.1 The intensity of illumination shall be measured in the plane of the standard image with the detector in the central area of the image. (See Paragraph 1.3.)
8.1.3.2 The detector shall have a spectral sensitivity matching as closely as possible the spectral sensitivity of the Type 1850-A iconoscope. A sufficiently close approximation is afforded by a Weston Photronic Cell, Model 594RB, equipped with a Corning filter, Type 5-51, 5562. (See Paragraph 1.3.)
8.1.3.3 The meter used with the Photronic Cell shall have a resistance of 20 ohms or less. Because the illumination pulse is of short duration and high peak intensity, the resistance of the meter will cause errors in measurement which increase rapidly with resistance value. For a 20ohm movement, the error will not exceed 2% over the anticipated range of intensities with the Weston Model 594RB cell. (See Paragraph 1.3.)
Field experience relating illumination in lEU's to satisfactory quality is as yet quite limited. It has not yet been possible to determine the number of lEU's which represent the line of demarcation between satisfactory and unsatisfactory performance.
P. 3 of 8 pp.
8.1.3.4 The combination of meter and cell shall be calibrated against a foot-candle standard using a blackbody source of illumination at 2700 K. (See Paragraph 1.3.) 8.1.4 The source of illumination shall be operated within any applicable ratings established by the manufacturer of the source.
8.2 Control of Intensity. It is probable that means for varying the intensity of illumination will be required for certain types of pickup tube. However, present information is not sufficent to permit the formulation of a standard.
8.3 Uniformity.
8.3.1 Intensity of illumination at any point in the area of the standard image shall be not less than 80% of the maximum intensity of illumination.
8.3.2 Upon replacement of an incandescent projection lamp, if such is used, no readjustment shall be required to achieve this distribution.
8.3.3 The receptive area of the lightsensitive element used for these readings shall have a diameter not greater than 5% of the picture width. No reading shall be taken with the center of the receptive element closer to the edge of the image area than 5% of the picture width.
8.4 Color. Although color of illumination may have significant effects on picture quality, present knowledge is not sufficient to permit the formation of a standard.
8.5 Flicker. Variation from pulse to pulse of the time integral of the illumination falling on any small area of the image may, under some conditions, give rise to visible flicker in the pic
NOT APPROVED
August 1952 Journal of the SMPTE Vol. 59
147