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- 12 - CALIBRATION OF TV STUDIO MATERIALS ty Harold Wright, Canadian Broadcasting Corporation (This paper is reproduced with the permission of the Canadian Broadcasting Corporation. Mir. Wright, who is Supervisor of Technical Instruction in the National Operations Office of CBC in Toronto, Canada, presented the paper at the Sixth Annual Conference of the Western Association ©f Broadcasters, held at Vancouver, B.C. March 2, 1956) INTRODUCTION In the design of settings for monochrome television programs the relative reflectances of the various paints, fabrics and other materials must be known in advance if the original concept of the design is to be maintained. A constant problem is the confusion of color contrast with bright¬ ness differences. Two colors of quite different hue, but each having the same reflectance will be reproduced as a single shade of gray and the tonal separation between the two will be lost. This has happened many times in television studios, usually to the embarrassment of the designer and others. This points up the need for an easy means of determining the relative reflectances of the various materials used. EARLIER METHODS Originally, the method for calibrating materials required two or more cameras together with studio facilities and the RETMA gray scale. Samples of paints and fabrics were placed under flat light and the nearest matching gray scale step was chosen with reference to the control room picture monitor. This was a cumbersome system with too many variables to ensure high accuracy. Lighting, video control, camera tube age etc. all combined to produce at times somewhat misleading results. It was felt that if all materials could be measured by a single instrument, results would be much more uniform. REFLEGTOMETER APPROACH The reflactometer, a device seldom found outside of research laborator¬ ies, will satisfy these requirements provided the instrument’s color response matches that of the camera tube. One of the simplest of these devices is the Baumgartner Reflectometer. A ten inch hollow metal sphere with a three inch opening in the bottom is fitted with a pair of light-sensitive cells and a small microammeter. The inside of the sphere is painted with a highly reflect¬ ive matt white paint so that it functions as a lifht integrating device. The light source is in the form of a small projector unit with lamp, condenser lens and objective lens. The main barrel of the unit is mounted on an offset swivel so that the light beam from the projector may be made to strike the wall of the sphere or bounce off a test sample under the bottom opening. These two conditions are illustrated in Fig 1 (a) and 1 (b). The brilliancy of the light source may be adjusted by means of a rheostat.