exposure vs light unit

exposure and light unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
exposure	Yes	No	No	No
light unit	Yes	No	No	No

As nouns, light unit is a hypernym of exposure; that is, light unit is a word with a broader meaning than exposure:

exposure (noun)	light unit (noun)
abandoning without shelter or protection (as by leaving an infant out in the open)	a measure of the visible electromagnetic radiation
the act of exposing film to light
presentation to view in an open or public manner
the act of subjecting someone to an influencing experience
a representation of a person or scene in the form of a print or transparent slide or in digital format
vulnerability to the elements; to the action of heat or cold or wind or rain
aspect resulting from the direction a building or window faces
the disclosure of something secret
the intensity of light falling on a photographic film or plate
the state of being vulnerable or exposed