Pretty as a picture

" To paint or photograph - that is the question:
Whether 'tis more to my advantage to color
Photographic accidents and call them painting,
Or squeeze the bulb against a sea of critics
And by exposure kill them? "
(Sadakichi Hartmann)

First seen in 1839, the earliest photographs caused such a sensation that many people hardly seemed to notice their most serious failure in reproducing reality: even the most pin-sharp and accurate Daguerreotypes - named after their French inventor, L. J. M. Daguerre - were only monochromatic. Daguerre himself was well aware of the short-coming and likened his pictures to drawings and engravings rather than to paintings. For a time, the comparison seems to have satisfied photographers and public alike.

But chemists and inventors were soon struggling to solve the problem; though many claimed to have found a solution, practical colour photography was not possible until 1905, a year after a perceptive and humorous critic wrote the above quotation. All 19th-century colour photographs are, in fact, hand-coloured - that is, overpainted. This book reproduces 131 examples, many in colour, treated with all sorts of substances, from oil and water colours to chalk and crayon.

Hand-colouring is, of course, a kind of retouching - improving a photograph by drawing or over-painting detail on to the negative or print. The practice dates from photography's earliest years, largely as a way of flattering the sitters. It was slightly less common with calotypes - invented in England rather than in France, on paper rather than on metal. Ironically, some paper prints by Henry Collen (the first professional calotypist and the first to colour calotypes) survive only because of their hand-painted elements: the photos underneath the paint have faded away.

Commercial photographers, realising that they had to persuade the public they were artists, decorated the mounts on which they sold their pictures with paint brushes, easels and palettes. But not everyone approved. Purists argued that it "adds nothing to the beauty of the picture, but, on the contrary, is decidedly objectionable"; others thought that, until nature provided a colour process, "it is no more of an intermeddling with her work to color a photographic image, than it is to dye cotton fabrics".

Famous photographers lined up on both sides. Julia Margaret Cameron, surely the greatest portraitist of the 19th century, boasted: "I am the only photographer who always issues untouched photographs, and artists for this reason, among others, value my photographs."

"Lewis Carroll", on the other hand, went to great lengths to find the best colourists in the country, especially for his portraits of nude girls.

In the United States, there was less controversy and overpainting was widely practised throughout the century. This book illustrates, for instance, many coloured tintypes from the fine collection of modern American photographer Olivia Parker: a soldier with buttons and sword picked out in gold, a farmer in front of the Stars and Stripes, babies with colourful flowers and ribbons. On these metal surfaces, viewers of the time must have found it difficult to credit they were looking at painted colours; this was even more true on the even surfaces of vases, plates and other ceramics.

The pinnacle of delicacy and realism was reached on magic lantern slides. Their glass surfaces were so smooth that the precise detail and subtlety of the painting could be convincing even when projected at many times the original size. Even today, it is sometimes hard to credit that the colours in the finest lantern slides are all applied with a paintbrush.

Heinz and Bridget Henisch tell the story of three-quarters of a century of overpainting with dedication and care. Their avowed aim is to reveal its "origins, techniques and aspirations" and they are perhaps least convincing in their aesthetic judgements, or lack of them. If the richness of detail, and the number of lengthy quotations from sources of the time, make this a rather dense read, it is difficult to imagine any reference book overtaking it as a source of information on the subject.

Colin Ford is director, National Museums and Galleries of Wales.