Virtually no photographs exist of any of the six death camps in operation (Auschwitz-Birkenau, Belzec, Chelmno, Majdanek, Sobibor, Treblinka). The Auschwitz Album, a collection of pictures made by an unknown German officer during the ‘‘selection’’ process on the Birkenau train platform, remains a notable exception.
In above photo, Jews undergoing the selection process on the Birkenau arrival platform known as the “ramp.”
On the other hand, several collections of photographs made during the 1941 Nazi execution campaigns across the western parts of the Soviet Union reveal not only the extent to which ordinary German soldiers (not the SS alone) participated in atrocities, but also the desire of Nazis, despite official prohibitions, informally to represent their crimes, and sometimes to use photography to humiliate victims.
There are also photos made by the resistance in the camps and then smuggled out.
Such as this (outdoors corpse burning at Auschwitz): http://www.holocaustresearchproject.org/othercamps/images/burning%20pits.jpg
Or this one (people inside a gas van at Chelmno): http://media-2.web.britannica.com/eb-media/44/67844-004-663ABC34.jpg