Patient to his doctor: "I have forgotten so many things lately, and it’s getting worse. What can I do?"
Doctor: "Yes, this is a known illness, unfortunately it has no cure. On that note, I'd like to remind you about the $800 that you owe me."
DaguerrotypeIn 1839, the daguerreotype photo process was announced at the French Academy of Science. Previous photographic processes required hours of exposure, but the daguerrotype (named after its inventor Louis Daguerre) needed only a few seconds. The plate was prepared with a layer of photo-sensitive silver halide, was exposed, developed using mercury vapour, and fixed in a solution of sodium hyposulphite. The image remains delicate, and must be protected under glass against damage by touching. The daguerreotype was produced with a direct positive image, needing no intermediate negative, but thus could not yield multiple reproductions made possible by later photographic processes.«[Image: first daguerrotype portrait in the Library of Congress collection. It shows a self-portrait of Robert Cornelius (1809-1893).] |
