While we cannot describe its appearance (the equivalent), we can define its function. When a photograph functions as an Equivalent we can say that at that moment, and for that person the photograph acts as a symbol or plays the role of a metaphor for something that is beyond the subject photographed.
Minor WhiteWhen I looked at things for what they are I was fool enough to persist in my folly and found that each photograph was a mirror of my Self.
Minor WhiteIf I have anything to give you through camera, it must be of myself. โฆ A gnawing burns inside โฆ to make something of myself worth giving.
Minor WhiteWhen I look at pictures I have made, I have forgotten what I saw in front of the camera and respond only to what I am seeing in the photographs.
Minor White...insight, vision, moments of revelation. During those rare moments something overtakes the man and he becomes the tool of a greater Force; the servant of, willing or unwilling depending on his degree of awakeness. The photograph, then, is a message more than a mirror, and the mans a messenger who happens to be a photographer.
Minor White