What device is used to measure the optical density of an exposed and processed film?

The device used to measure the optical density of an exposed and processed film is a densitometer. Optical density is a logarithmic measure of the amount of light transmitted through the film, and understanding it is crucial for evaluating the quality of radiographic images. A densitometer quantifies the density of the film by measuring the intensity of light passing through the film and comparing it to the intensity of light before it passes through. This allows technicians to assess whether the film has been adequately exposed and processed, which is vital for achieving the desired contrast and visibility in radiographic imaging.

Other devices mentioned serve different functions; for example, a photometer measures light intensity without providing a density measurement for film. A caliper is primarily a measuring tool used to determine physical dimensions, and a spectrometer analyzes the physical properties of light but does not specifically measure the optical density of films.