Archived posting to the Leica Users Group, 2011/05/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Peter writes: http://www.bbc.co.uk/news/13411083 I think that photograph of a tartan ribbon is a remarkable thing. - - - - - - Photographic technologists have a lot of questions about how James Clerk Maxwell could take a full color photograph using plates that were insensitive to red light. All photographic materials were only blue sensitive at that time although some green could be recorded. Orthochromatic film, fully sensitive to green light was not introduced until 1879 and panchormatic film, sensitive to red light was not developed until the 1890s. Orthochromatic film was widely used through the 1930s. Old timers will remember that orthochromatic film could be handled freely in a darkroom under a red safelight without damage. The conclusion was that red dye in the tartan ribbon was not a pure red but reflected ultraviolet light as well. The filter through which the "red" plate was exposed passed ultraviolet light also, permitting a "red" image to be recorded. When the plate was projected through a red filter, a red image appeared on the screen. Maxwell's photo was a pseudo colored picture rather than the real thing although it fooled the photographic community for over 100 years. Larry Z