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. 

This  deliberate authorial abnegation  had an  interest in the nonart nature of photography, whether professional or amateur, as a new resource or horizon of possibility for avant-garde artistic practice in a climate of increasing commercialization. That is, many artists valued photography in all the respects in which it seemed to evade, rather than mimic, art with a capital A—hence photography's standing as the pictorial equivalent of the readymade.

The widespread recourse in contemporary art to the scrappy snapshot  represents a  rejection of  aesthetic ideology and  the institutional authority associated with the decay of US style modernism.   This rejection of modernist categories referred to the Kantian model of the art object’s disinterestedness; the Greenbergian claim of  an aesthetic as well as a moral distinction between high art (painting) and kitsch; the appeal to originality,  creative mastery or genius;  formalism,  the centrality of beauty and the contemplative art object.    

The  machine print snapshot was identified by artists as a kind of constitutive marker of avant-garde identity. Postmodernism, for instance, in its  deconstruction of  the author, identity, and representation unblocked some of the cultural prejudices and assumptions  of Modernist theory.   However,  this negation of  aesthetic ideology  the name of photography and the anti-aesthetic  no longer seems plausible in the light of the general incorporation of photography into the category of art by the art institution.