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.
If there is any question as to the location of the light source, the operator's manual for the sensitometer should be consulted.
Was the emulsion facing the sensitometer light source?
Developing a master sensitometer has proven to be more difficult than expected, but manufacturers have produced "reference sensitometers" that are matched within 1% of an ideal reading and within 2% of each other.
Equipment such as sensitometers and densitometers must have a tight range of repeatability and must provide information on long-term stability.
Medical physicists, government regulators and others who check the medical facility's QA/QC programs must use calibrated sensitometers that are recertified every 2 years by a licensed laboratory.