Which of the following best defines 'contrast sensitivity' in visual terms?

Contrast sensitivity refers to the eye's ability to discern between different levels of light and dark, or luminance. This is essential for recognizing objects in varying lighting conditions, particularly when they blend into the background. In practice, contrast sensitivity allows individuals to see details more clearly when the difference in brightness between the object and its surroundings is subtle.

For example, during dusk or in fog, having a high level of contrast sensitivity would allow a person to identify and distinguish objects that are not strikingly different from their background. Thus, being able to detect differences in luminance is a critical aspect of visual perception, impacting how we navigate and interact with our environment.