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NEGATIVE EXPOSURE CONTROL' DON NORWOOD**
Summary. — It would be desirable to have negative exposure control on the basis of an exact science. Toward this end the functioning of the eye as it views a subject and the photographic reproduction of the subject is studied. The brightness of the subject is broken down into its components of reflectance (a constant) and incident illumination (a variable). The eye compensates for changes in the illumination. The "tone" of the object is based on its reflectance. It is this that determines the print density used to portray the object. Between the subject's fixed reflectance and the print's fixed density lies the variable of negative density.
A system is proposed whereby given reflectance in the subject is represented by fixed density in the negative. Operation of the system involves negative exposure control by measurement of incident light. Measurement of effective incident illumination is accomplished by a photoelectric meter specifically designed to respond to the threedimensional characteristics of incident illumination. The system is free from many of the influences which tend to cause undesirable variations and errors in negative exposure. It provides a means of putting negative exposure control on the basis of an exact science.
Every time his camera shutter clicks, probably every photographer utters a little inward prayer to the effect that, "Please may the exposure be right!" For once the shutter has clicked, the die is cast, the Rubicon has been crossed, the deed has been done. Thereafter all the king's horses and all the king's men can not appreciably improve the effect of that exposure. The quality, not only of the negative, but also of the print to be made therefrom, depends in large measure upon the correctness of that exposure. Thus it will be appreciated that negative exposure control is a subject of considerable importance to every photographer.
If negative exposure control had the status of an exact science, the photographer would be able to take for granted that his exposures would be correct every time. As a step toward this very desirable objective, the purpose of this paper is to discuss various phases of negative exposure control. It is hoped to clarify to some
* Presented at the 1940 Fall Meeting at Hollywood, Calif. ; received October 1, 1940.
** Hollywood, Calif.
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