In most cases not involving million dollar budgets, human observer has 
no diffuculty telling whether a given image is a photograph or was it
generated by a computer. Qualitative understanding why computer graphics
images differ from natural ones is a difficult problem. In this talk, I
will present two recent projects which deal with obtaining such
information and using it to the advantage of computer graphics. The 
first project explores second order image statistics as a possible source of
significant deviation between photographs and rendered images while the
second suggests a simple way to transfer color information from a
photograph to a computer generated picture.