What tool is used to test film fixer retention?

The correct answer involves the use of a test kit specifically designed for assessing film fixer retention. This tool is essential in radiography to ensure that the fixer, a chemical used in the film development process, is functioning effectively. Proper fixer retention is crucial because inadequate fixing can lead to residual undeveloped silver halides remaining on the film, ultimately affecting image quality and reducing film longevity.

A test kit typically includes various components such as chemical indicators and procedures to measure the effectiveness of the fixing process and to confirm that the fixer is adequately removing unwanted materials from the film. By using this tool, operators can determine if the fixer is still effective or if it needs to be replaced, ensuring that photographic quality meets necessary standards for radiographic work.

The other tools mentioned, such as photometers, digitizers, and density meters, serve different purposes. A photometer measures light intensity, a digitizer converts analog signals into digital data, and a density meter evaluates the optical density of films but does not specifically measure fixer retention. Thus, they do not fulfill the specific requirement of assessing film fixer retention.