The Probert Encyclopaedia of Science & Technology

CAMERA OBSCURA

Camera obscura was the original name, used around 1900, for what we now call simply a camera. The original camera obscura was an optical instrument employed for exhibiting the images of objects in their forms and colours, so that they may be traced and a picture drawn, or may be represented by photography. A simple camera obscura is presented by a darkened chamber into which no light is permitted to enter excepting by a small hole in the window-shutter. A picture of the objects opposite the hole will then be seen on the wall, or on a white screen placed opposite the opening. Rays of light passing through a convex lens being reflected from a mirror (which is at a slope of 45 degrees) to a glass plate where they form an image that may be traced. Another arrangement is a kind of tent surrounded by opaque curtains, and having at its top a revolving lantern, containing a lens with its axis horizontal, and a mirror placed behind it at a slope of 45 degrees, to reflect the transmitted light downwards on to the paper.
Research Camera Obscura