exposure locus

a. subjecting a sensitive surface to light (visible or not), and its duration; b. state of being uncovered or unprotected; c. being subject to the elements; d. disclosure, revelation, visibility, or the risk thereof.

Getty AAT: The act of presenting a photosensitive surface to actinic rays or radiant energy, especially light; and the extent of radiant energy received in this context. (AAT 300191218)