A densitometer is an instrument used for measuring and reading the density of film and paper directly. Film is read on a transmission densitometer, and paper is read on a reflection densitometer. Most densitometers supplied by the Navy today have both transmission and reflection reading capabilities on the same meter (fig. 10-26).

A densitometer uses a photoelectric cell to measure the light transmitted through film or reflected from paper electronically. Before a densitometer can be used, it must be checked and calibrated against a reference standard. To use the meter, you must place the material to be measured, emulsion-side up, in the light beam between the source and the photocell. The density reading is then read directly from the meter.

There are several sets of filters incorporated in the head of the densitometer. When you are reading black-and-white materials, the yellow filter must be in place. When color materials are read, there are two different sets of filters that are used. They are Status A and Status M filters. Status A filters are used to read color transparencies and prints. Status M is used to read color negative film that has an orange mask

Only certain steps of the control strip are read. The steps that you are required to read are established by the manufacturer of the material or are established by the quality control technician within your imaging facility. When you are reading the steps on your control strip, be sure that the emulsion side is facing up and take the reading from the center area of each step (fig. 10-27).