NIST reference densitometer for visual diffuse transmission density

The Optical Technology Division of the National Institute of Standards and Technology has developed a new reference densitometer for measuring visual diffuse transmission densities using the diffuse influx mode. This densitom eter is used to calibrate both x-ray and photographic film step tablet Stan dard Reference Materials. The design, characterization, and operation of th e densitometer are detailed. The densitometer was fully characterized both to verify compliance with the applicable documentary standards and to deter mine the combined uncertainty in transmission density associated with the c alibrations.