Since the time of Sir Isaac Newton (1643–1727), when the spectrum first became a research object in its own right and shook off its bad reputation as a disturbing, even frightful phenomenon, the recording of the coloured spectrum in its full variegated glory proved to be a protracted challenge (Hentschel 2002). Various techniques were tested out and used, among them woodcut, copper engraving, and lithography, and, since 1839, also photography. In the early nineteenth century, hand-colouring of engravings produced some of the most impressive results (such as here in Fig. 4).

However, hand-colouring depended on the skill of the artist in capturing the subtle gradations of tone. Such high-quality plates were consequently rare and not reproducible at the time. Chromolithography, which was widely practised since the 1830s, took a substantial step forwards, but the generation of colours by superpositions of layers of various printed primary colours (up to six) remained insufficient. Daguerreotype, talbotype, and other early forms of photography all had the disadvantage of being recordings in black and white. Furthermore, early photography had severe problems with colour sensitivity, especially in problematic colour ranges such as orange or green. The solar spectrum actually served as the preferred test object for every new photographic process. The resulting exposure directly displays the relative sensitivity to the different components of the continuous spectrum. Any broader gaps in the bright continuous spectrum became immediately visible. Thus, the main goal of spectroscopists and photographers alike was to obtain a faithful representation of the whole spectrum in colour.