In the first stage, members of the DIN committee, including representatives of the government, medical professions, film companies, processor equipment companies and testing equipment manufacturers, decided to develop a "master" sensitometer
. The DIN members concluded that only the use of calibrated test equipment would permit an institution's film processing to be judged fairly.
This verification, called the Sensitometer Technique for the Evaluation of Processing or STEP test, is a comparison of the sensitometric values from an FDA control film processed in the facility's processor using the facility's normal processing cycle to values from the same type of film run in a processor known to be operating at manufacturer's specifications.
To establish operating levels, a film from the control box is exposed using the sensitometer. It is vital that the sensitometer's color switch is set to green for orthochromatic film and that the emulsion side of the film is facing the light source of the sensitometer.
Was the emulsion facing the sensitometer light source?