Hermann Wilhelm Vogel

Hermann Wilhelm Vogel with his Camera image by Photo_History (Image rights)

Hermann Wilhelm Vogel (*1834 Dobrilugh, Niederlausitz, †1898 Berlin, Charlottenburg) was born as a son of a textile merchant. He studied physics and chemistry and at the age of 24 years he became an assistant at the Mineralogy Institute of the University of Berlin, where one of his duties was photographing minerals. Vogel established the Photographischen Verein zu Berlin (Photographic Society of Berlin) in 1863, while his Photographischen Mitteilungen magazine printed from 1864 was one of the first photographic magazines of the world. In 1879 Vogel became a professor of photochemistry at the Technical University of Berlin.

In the autumn of 1873, Vogel discovered accidentally the optical sensitization phenomenon of color-blind emulsion, which eventually led to development of orthochromatic emulsion. On August 25, 1873 he conducted an experiment to establish actual spectral sensitivity of silver halide, using two - wet and dry - photographic plate types. To his surprise, the dry plate of the Stewart Wortley company presented some sensitivity increase for the wavelengths longer than blue light. Researching this issue, Vogel discovered that the sensitivity increase was caused by yellow dye added to the emulsion as the anti-reflective measure. In course of further research he prepared photosensitive emulsion with yellow Korallin dye added, which absorbed wavelengths from 510 to 590 nm. As a result the emulsion was sensitive to yellow light almost as highly as to blue light. Conclusions from this research were published under the title "On the sensitiveness of bromide of silver to the so-called chemically inactive colours". During further work Vogel developed dry photographic plates sensitized with the Eosin dye and in the same year the name "orthochromatic" was used for the very first time for dry plates sensitized by Eber with the Eythrosin sensitizer. Also in 1884, Vogel discovered that a mixture of Cyanin and Chinolinrot, he called Azalin, sensitizes emulsion up to reddish orange light. As the result of Vogel's work panchromatic emulsion was developed and a number of sensitizing dyes were invented around turn of the century by numerous researchers as Valenta, Miethe, Traube and Koenig.

Sources

• Kleffe H.: Aus der Geschichte der Fototechnik; VEB Fotokinoverlag Leipzig, Leipzig, 1983.