Panchromatic film is a type of black-an-white photographic film that is sensitive to all wavelengths of visible light. A panchromatic film therefore produces a realistic image of a scene. Almost all modern photographic film is panchromatic, but some types are orthochromatic and are not sensitive to certain wavelengths of light. As naturally prepared, silver halide emulsions are 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. However, his technique was not extended to achieve a fully panchromatic film until the early 1900s, shortly after his death.