Xlg Secret Pictures
Spy camera tricks from Popular Science 1934-

TRICKS used by press photographers and detectives come in handy when it is desired to snap imposed photographs of friends or members of the family. For such pictures photographers usually use tiny, easily concealed cameras. Despite their size, these midget cameras are surprisingly fast and accurate, and their wide angle lenses make the use of a range finder unnecessary. One of the commoner ways of screening a camera from the intended subject is to cover it with a handkerchief until the trigger is released. Occasionally the camera is carried in a vest pocket with the lens shielded by the wearer’s coat.

Modern Mechanix » Tricks That Enable You to Take Secret Pictures – Link.