The drawing of the camera obscura reminds me of something my
older brother and I did as kids. We made a box camera with a
lens from a broken film camera and used blue print paper as
our film. Blue print paper is developed with ammonia vapor;
a very simple and forgiving process. Because of the insensitivity
of blue print paper, exposures were on the order of minutes
under the best of conditions. Needless to say, we didn't do
too many portraits with it!