3.4 Indexing
Selecting an image a point of reference for another object by physical connection
In theorising about the differences among the sign types- symbol, icon and index- C.S. Peirce distinguishes photographs from icons even though icons (signs which establish meaning through the effect of resemblance) form a class to which we would suppose photographs belong.
“Photographs”, Peirce says, “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 (indices), that point to a physical connection with a particular historical juxtaposition of people and place”.  
The work of the Victorian prize-winning photographer Frank Meadow Sutcliffe provides examples of both indices and icons.  The latter are outdoor group portraits of the local people of Whitby and its surrounding district.  Mainly to produce a genre effect, but also because of the slow exposure values of his photographic emulsion, Sutcliffe posed his subjects ‘unnaturally’ to produce a balanced picture.  His artifice in composition as never been surpassed.