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Sensitometry - 14209_281

 
  
 
Figure  10-24.–EG&G  sensitometer. Courtesy of EG&G, Inc. 302.288X these measurements are through sensitometry and densitometry.  When  sensitometry  and  densitometry  are used, variations from the standard and the corrections recommended are expressed in numbers, not in terms of personal  opinion. SENSITOMETRY Sensitometry is the science of determining the photographic   characteristics   of   light-sensitive materials. In sensitometry, special test or control strips are prepared by accurately exposing the material with varying amounts of light. These test strips are then processed. A sensitometer is an instrument used to produce the special  test  strips  called  sensitometric  strips.  A sensitometer  is  used  to  produce  these  sensitometric strips  because  it  provides  consistent  and  repeatable exposures of a known quantity and quality of light. The sensitometer is used to expose a strip of film with varying amounts of known exposure on the same strip of film. Since the sensitometer provides repeatable exposures  each  time,  any  changes  in  density  indicates  a change  in  processing.  In  Navy  photography,  the sensitometer  is  used  to  expose  black-and-white materials only. There are several uses for sensitometric strips; but in this training manual, we are only concerned with monitoring a process. Here the sensitometric strips are used as control strips. Control strips are made and processed under the controlled conditions of time, temperature,  and  agitation.  This  is  true  for  both black-and-white and color materials. Black-and-white control strips are usually made in the photo lab, while color  control  strips  are  obtained  by  the  manufacturer  of each  material. Ideally, a sensitometer should be designed so you can  accomplish  the  following  objectives: 1. Predetermine the total amount of exposure. 2. Determine the difference in exposures given to various  areas. 3. Control the color quality of the light. 4.  Consistently  reproduce  or  duplicate  the  same lighting  conditions. 5. Provide a wide range of exposures. The  sensitometer  used  most  commonly  in  the  Navy today is the Egerton, Germeshausen, and Grier (EG&G) sensitometer (fig. 10-24). This sensitometer uses a 10-39


   


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