What is a group of Brightnesses called?

A group of brightnesses is commonly called a Range.

Collective nouns are words used to describe a group or collection of specific objects, persons, or things. When it comes to describing brightnesses - the degree of luminosity or the intensity of light - a suitable collective noun does not exist. However, we can formulate a phrase or expression to convey the concept of a group of objects or sources of brightness. For instance, if we wanted to describe a collection of brilliantly lit objects, we could use the phrase "a constellation of brightnesses." This expression evokes the idea of multiple sources of light shining together, like stars united in a constellation, illuminating the surroundings. Alternatively, we could refer to a "cluster of brightnesses," which conveys a group of shining objects gathered closely together. This phrase suggests a concentration of luminous sources creating an intensified overall brightness. Another possibility is stating a "flood of brightnesses." This expression imparts a sense of an overwhelming amount of light emanating from various sources, enhancing the surrounding area with radiance. While collective nouns specifically designed to describe brightnesses are not commonplace, expressing the idea through inventive and descriptive phrasing allows us to convey the essence of multiple sources of light shining in unison or in close proximity.