April 14, 2011
Silver halides are used in photography from over 100 years; silver halides are sensitive up to 500 nm that is small part of visible spectrum (400 to 700nm). To increase the sensitivity in whole visible spectrum, various dyes were added and this is called spectral sensitization. In 1856, C.H. Greville Williams invented first cyanine dyes and in 1857, H. W. Vogel used the cyanine dyes because of their good photosensitivity.