a darkened boxlike device in which images of external objects, received through an aperture, as with a convex lens, are exhibited in their natural colors on a surface arranged to receive them: used...
Call me a nit-picker, but the camera obscura was not really a camera in the sense that it was not invented for the purpose of making photographs, and cameras don't develop pictures. If you're asking...
usually it looks like a wooden box with a lens on one side and a mirror at a forty five degree angle inside that will allow you to see the image when you look at the metal plate