SM015     Photographic plate camera     circa 1940     Light

  Photography is the art of producing permanent images of objects by utilizing the changes that certain substances undergo in the presence of light.

  The darkening effect of light on silver chloride was known to the alchemists of the sixteenth century.   In 1802 Thomas Wedgewood and Humphry Davy published a paper on producing profiles on glass plates utilizing silver nitrate.

  In 1810 Seeback produced an image of the solar spectrum on paper coated with silver chloride with intensity proportional to the actual intensity of the various colours.

  In 1814 Niepce used a process called ‘heliographie’ using a metal plate coated with bitumen in oil of lavender and exposing in a camera using a process of development of the plate after exposure.   In 1839 Daguerre in Paris and Fox Talbot in England published details of their respective practical processes of producing images by photography.

  In 1850 Archer and Fry produced pictures using collodion as the carrier of the sensitive emulsion with very good results.   In 1871 Dr. Maddox demonstrated that the sensitivity of the emulsion is increased if gelatine is used as the emulsifying agent.   Gelatine emulsions on glass and paper can be exposed dry and chemically developed afterwards.   So the image of the camera can be permanently fixed as a silver image.

  The photographic lens, which played such an important part in photography, was invented in the earliest years.   William Wollaston invented the first lens in 1812.   In 1831 Charles Chevalier made an improved lens using flint glass to correct aberrations.   Joseph Petzval invented a faster lens in 1841 using a combination of telescope objectives with a space between the elements. 

  Daguerre