The specificity of media is analyzed in the context of post-modernist art in the late seventies and eighties, particularly in the context of photography and its role in new media and the problem of “the invention of the medium” by Rosalind Krauss and general understanding of the me- dium as a convention. Krauss’s attitude is different from Michael Fried’s ‘mediality of images’ (not only photographic images). Fried’s ideas of “theatricality” and “exposition” are different from Krauss’s ideas. Also, non-artistic strategy of ‘separation of realities’ is analyzed in the same context. “True” and “false” elements are combined in pictures just like “authentic” documents are combined with theatrical images, paintings with photographs and modernism with post-modernism.