The Basic Principles of Daguerre's Photography

Daguerre photography is also called "silver photography". Originated by French Daguerre, it was published in 1893 and began to be used around 1860. This is the earliest photography method with practical value in the history of photography. This is a direct positive method that appears on silver-plated copper plates and cannot be printed and reproduced. The basic method is to plate silver on the polished copper plate and smoke the silver surface with padding steam to produce photosensitive silver iodide. Put this photosensitive silver plate in the cassette for later use. When shooting, this kind of silver disk is put into a square box camera with a lens aperture of F3.6, and the exposure time is about 1 minute. After shooting and exposure, the silver surface was developed by mercury vapor fumigation. In the light-receiving part of the silver plate, mercury and silver form a shiny amalgam, forming a bright part of the image. The unexposed part of the silver plate has no amalgam and still exists in the form of silver iodide. After development, the silver plate was fixed with baking soda solution, and silver iodide dissolved, showing a black copper plate, which constituted the dark part of the image.

The "photo" produced by Daguerre silver plate method is a positive image recorded on a silver-plated copper plate. It has good clarity, delicate images and good preservation. Because it is essentially a relief image made of mercury, it will produce different effects from different angles.