The use of the Leica has traditionally been associated with photojournalism, street photography and photographic realism. Realism is usually interpreted  in terms of the   positivist understanding of knowledge  as an edifice  based on fact and observation, the objectivity claimed by foundational epistemology, and the universality  of the view from nowhere or the God's eye view. 

The philosophical underpinnings of this positivism can be found in photography's  indexical relation,  which is  taken to distinguish photography from other forms of picture making. The inference drawn  is that an image of the world is formed automatically, without the creative intervention of  the human being. Consequently, images made by strictly photographic means are solely causal traces of the objects responsible for them.

Philosophers of photography  in the analytic  aesthetic tradition develop this theme. Thus  Kendall Walton in his  “Transparent Pictures" paper claims that photographs are transparent. He argues  that  we literally, if indirectly, see through photographs to what they are photographs of,  because photographs do not depend on the mental states of the photographer but simply record how things stood in a given portion of the world at a given time. 

Walton relies on a distinction between mechanical and intentional production to distinquish between photographs and other kinds of still images, such as painting. Whatever the controversy concerning Walton's claim that photographs are transparent the assumption underlying this  account is that photographic depiction is independent of the intentions of the photographer in the respect that counts. The mechanical, causal, or “mind-independent” nature of the photographic process taken to distinguish photography from other modes of depiction works off the  dominant conception of photography as an automatic recording mechanism.    

Analytic philosophers such as Walton tend to take something like the snapshot (that is, an automatically recorded image) as paradigmatic of how photography in general works and so  face difficulties doing full justice to the actual artistic uses of the medium, given that their underlying assumptions about photography preclude the possibility of fully fledged photographic art.  

Thus  what the seventies generation of fully fledged conceptual artists who made extensive use of photography—such as Douglas Huebler, Keith Arnatt, John Hilliard, and Victor Burgin—followed by the eighties pictures generation of artists--- such as Cindy Sherman, Sherrie Levine, and Richard Prince--- had in common, for all their other differences, was  an interest in the photograph as a kind of pictorial readymade that can be appropriated and repurposed in ways that limit authorial control.