Early colour photos reveal photographer's chemical craft
High power analysis unmasks chemicals used to create 19th century images
A set of early colour photographs taken by the 19th century photographer Louis Ducos du Hauron has undergone chemical analysis by heritage scientists in France. The investigation has enabled them to identify which techniques were used to take the photographs, and in some cases when they might have been taken.
Early colour photography was a long, painstaking process. The image would have to be captured as three negative shots through different coloured filters, which were then developed on gelatin films containing red, blue and yellow pigments. These prints then had to be assembled into a single print to get an image with the full spectrum of colours.