Mary Ann Doane writes that "indices have no resemblance to their objects" (the semiotics term for one that does is an "icon")
Yet C. S. Peirce, confusingly, situates "photography as primarily indexical, subordinating the iconic dimension to secondary status. Photography’s iconicity [is] a by-product of its indexicality" (Doane's explanation)
Peirce: "Photographs, especially instantaneous photographs, are very instructive, because we know that they are in certain respects exactly like the objects they represent. But this resemblance is due to the photographs having been produced under such circumstances that they were physically forced to correspond point by point to nature. In that aspect, then, they belong to the second class of signs [indexes], those by physical connection."
Doane: "For Peirce, the iconicity of the photographic image is reduced by the sign’s overadherence to its object (elsewhere he claims that an icon, in order to resemble its object, must also be noticeably different)."