It is often said that it was the painters who invented Photography (by bequeathing it their framing, the Albertian perspective, and the optic of the camera obscura). I say: no, it was the chemists. For the noeme "That has been" was possible only on the day when a scientific circumstance (the discovery that silver halogens were sensitive to light) made it possible to recover and print directly the luminous rays emitted by a variously lighted object.
The photograph is literally an emanation of the referent.
From a real body, which was there, proceed radiations which ultimately touch me, who am here; the duration of the transmission is insignificant; the photograph of the missing person, as Sontag says, will touch me like the delayed rays of a star. A sort of umbilical cord links the body of the photographed thing to my gaze:


Light, though impalpable, is here a carnal medium,
a skin I share with anyone who has been photographed.