The significance of photography as a medium—or what makes photography a single, unified medium—was a key idea in modernist aesthetics that was centred around formalism and the autonomous art object that was designed to be stored in art galleries/museums as part of our society’s cultural heritage.
The shift in critical discourse, initiated by postmodernism, has been away from photography per se, to the more generic term picture. The latter term encompasses a range of pictorial arts (including, in principle, moving pictures) and thereby disavows in advance any strong (or narrow) conception of medium specificity.
Associated with this shift away from Greenberg modernism from the 1960s to the 1980s is the preference for unpretentious snapshot effects, documentary value, and deadpan anti-aesthetic qualities, as well as in their use of photography for appropriating and recycling existing imagery. This tendency or conceptualism trajectory had an interest in the photograph as a kind of pictorial readymade that can be appropriated and repurposed in ways that limit authorial control.