This study aims to examine the main issues of photography regarding digital technology. If the photography in the analog era depends on the concept of ‘document’, ‘record’, ‘reel’, ‘trace’, etc., the photo in the digital era is explained by the concept of ‘simulacrum’, ‘fiction’, ‘virtuality’, etc. We know that these concepts are incompatibles. So, the photograph don't have the classic position of trace of reel in the digital era so-called ‘post-photography’. Accordingly, main questions of theory of photography require a modification. The core is the theory of index that led the discussion about photography since 1980'. This theory was, in fact, predominant in the analog ara, but has a apparent limit.
There is two viewpoints which admit this limit : the one accept partially the theory of index. According to this, digital photo is not different, ‘intrinsically’, from analog photo. The other that admit a fundamental difference of both sides call for revision of index paradigm. In principle, analog is continuous(resemblance), digital is discontinuous(difference). But, resemblance and difference are, ultimately, not sameness. That is inherent quality of all photographic image(analog, digital).
The theory of index had a compulsive impulse to determine the specificity of photography. But, even if a photograph has some characteristic of index, it can not be identified to index. Rather it has various characteristic of image. Thus simulacrum of post-photography is not originally new. Therefore, we can suggest, according to the thought of Bazin, as follows : if the painting is liberated from compulsion of realism by the invention of photography, the photography is liberated from compulsion of index by digital technology.