As naturally prepared, a silver halide photographic emulsion is much more sensitive to blue and UV light than to green and red wavelengths.
The German chemist Hermann W. Vogel found out how to extend the sensitivity into the green, and later the orange, by adding sensitising dyes to the emulsion.
By the addition of erythrosine the emulsion could be made orthochromatic while some cyanine derivatives confer sensitivity to the whole visible spectrum making it panchromatic.
Kenneth Mees credits Wratten & Wainwright with preparing the first commercial plates with panchromatic emulsions.
[6] But early panchromatic stock was more expensive, had a relatively short shelf-life, and was more difficult for laboratories to process because it required working in total darkness.
[7] Digital panchromatic imagery of the Earth's surface is also produced by some modern satellites, such as QuickBird, Cartosat and IKONOS.