Being able to differentiate between an object and its background (Course Material/PenetrantTest/Introduction/contrastsensitivity.htm)

the ability to differentiate between an object and its background.

Ability to perceive a lightness or brightness difference between two areas. Frequently measured for a range of target patterns differing in value along some dimension such as pattern element size and portrayed graphically in a contrast sensitivity function in which the reciprocal of contrast threshold is plotted against pattern spatial frequency or against visual angle subtended at the eye by pattern elements (such as bars).

The smallest thickness change in specimen which produces a descendible change in optical density on a:, radiographic (or radioscopic image, usually expressed as a percentage of the total specimen thickness.'

The smallest thickness change in specimen which produces a discemible change in optical density on a:, radiogragphic (or radioscopicl image, usually expressed as a perceatageof the total specimen thickness.'

A measure of the least amount of contrast detectable by the eye.

The least amount of contrast that you can still see.