"In 1839, Louis Daguerre presented the first practical process of photography to the French Academy of Sciences. Unlike earlier photographic methods, his daguerreotypes had stunning quality and detail and did not fade with time. Artists adopted the new technology as a new way to depict the nude form, which in practice was the feminine form. In so doing, at least initially, they tried to follow the styles and traditions of the art form. Traditionally, an académie was a nude study done by a painter to master the female (or male) form. Each had to be registered with the French government and approved or they could not be sold. Soon, nude photographs were being registered as académie and marketed as aids to painters. However, the realism of a photograph as opposed to the idealism of a painting made many of these intrinsically erotic.

The daguerreotypes were not without drawbacks, however. The main difficulty was that they could only be reproduced by photographing the original picture since each image was an original and the all-metal process does not use negatives. In addition, the earliest daguerreotypes had exposure times ranging from three to fifteen minutes, making them somewhat impractical for portraiture. Unlike earlier drawings, action could not be shown. The poses that the models struck had to be held very still for a long time. Because of this, the standard pornographic image shifted from one of two or more people engaged in sex acts to a solitary woman exposing her genitals. Since one picture could cost a week's salary, the audience for these nudes mostly consisted of artists and the upper echelon of society. It was cheaper to hire a prostitute and experience the sex acts than it was to own a picture of them in the 1840s.3 Stereoscopy was invented in 1838 and became extremely popular for daguerreotypes, including the erotic images. This technology produced a type of three dimensional view that suited erotic images quite well. Although thousands of erotic daguerreotypes were created, only around 800 are known to survive; however, their uniqueness and expense meant that they were once the toys of rich men. Due to their rarity, the works can sell for more than 10,000 GBP. In 1841, William Fox Talbot patented the calotype process, the first negative-positive process, making possible multiple copies. This invention permitted an almost limitless number of prints to be produced from a glass negative. Also, the reduction in exposure time made a true mass market for pornographic pictures possible. The technology was immediately employed to reproduce nude portraits. Paris soon became the centre of this trade. In 1848 only thirteen photography studios existed in Paris; by 1860, there were over Most of them profited by selling illicit pornography to the masses who could now afford it. The pictures were also sold near train stations, by travelling salesmen and women in the streets who hid them under their dresses. They were often produced in sets (of four, eight or twelve), and exported internationally, mainly to England and the United States. Both the models and the photographers were commonly from the working class, and the artistic model excuse was increasingly hard to use. By 1855, no more photographic nudes were being registered as académie, and the business had gone underground to escape prosecution. The Victorian pornographic tradition in Britain had three main elements: French photographs, erotic prints (sold in shops in Holywell Street, a long vanished London thoroughfare, swept away by the Aldwych), and printed literature. The ability to reproduce photographs in bulk assisted the rise of a new business individual, the porn dealer. Many of these dealers took advantage of the postal system to send out photographic cards in plain wrappings to their subscribers. Therefore, the development of a reliable international postal system facilitated the beginnings of the pornography trade. Victorian pornography had several defining characteristics. It reflected a very mechanistic view of the human anatomy and its functions. Science, the new obsession, was used to ostensibly study the human body. Consequently, the sexuality of the subject is often depersonalised, and is without any passion or tenderness. At this time, it also became popular to depict nude photographs of women of exotic ethnicities, under the umbrella of science. Studies of this type can be found in the work of Eadweard Muybridge. Although he photographed both men and women, the women were often given props like market baskets and fishing poles, making the images of women thinly disguised erotica. Parallel to the British printing history, photographers and printers in France frequently turned to the medium of postcards, producing great numbers of them. Such cards came to be known in the US as "French postcards"." :Wikipedia.