Hermann W Vogel (1834 - 1898)

In the earliest days of photography, photographic emulsions were sensitive only to blue and white light, giving incorrect tonal values, with red and green objects appearing very dark. Vogel (Figure 7), a German chemist, made a major contribution to the development of colour photography when, in 1873, he discovered that if he added appropriate dyes when making a solution, the plates would respond to green light (essential, obviously, for landscape photography). This led to the manufacture of "orthochromatic" plates (sensitive to all the visible spectrum except red and deep orange).

Figure 7 (left). Hermann W Vogel.

According to Gernsheim (1961) Vogel accidentally discovered the application of short-wavelength photography to medicine in 1864 when he observed black spots on the face of a portrait of a woman - spots that were at the same time hidden to the naked eye (Figure 8). A few days after the photography, however, the woman was found to have smallpox. Films at that time of course were only sensitive to blue/ultraviolet light and they would have naturally enhanced the rendition of any skin condition. The significance of Vogel's discovery was not recognized at the time and it would be another forty years before invisible radiation photography was truly 'born'.

Figure 8 (left). Early signs of smallpox visible in blue/ultraviolet sensitive film from 1864.

References:

• Gernsheim, A. 1961, "Medical photography in the nineteenth century," Med. Biol. Illustr.: 11(3): 147 -156.

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