Talbot invented the first process for creating reasonably light-fast and permanent photographs that was made available to the public, although his was neither the first such process invented nor the first one publicly announced.  

Shortly after Louis Daguerre's invention of the daguerreotype was announced in early January 1839, without details, Talbot asserted priority of invention based on experiments he had begun in early 1834. At a meeting of the Royal Institution on 25 January 1839, Talbot exhibited several paper photographs he had made in 1835. Within a fortnight, he communicated the general nature of his process to the Royal Society, followed by more complete details a few weeks later. Daguerre did not publicly reveal any useful details until mid-August, although by the spring it had become clear that his process and Talbot's were very different.

Talbot's early "salted paper" or "photogenic drawing" process used writing paper bathed in a weak solution of ordinary table salt (sodium chloride), dried, then brushed on one side with a strong solution of silver nitrate, which created a tenacious coating of very light-sensitive silver chloride that darkened where it was exposed to light. Whether used to create shadow image photograms by placing objects on it and setting it out in the sunlight, or to capture the dim images formed by a lens in a camera, it was a "printing out" process, meaning that the exposure had to continue until the desired degree of darkening had been produced. In the case of camera images, that could require an exposure of an hour or two if something more than a silhouette of objects against a bright sky was wanted. Earlier experimenters such as Thomas Wedgwood and Nicéphore Niépce had captured shadows and camera images with silver salts years before, but they could find no way to prevent their photographs from fatally darkening all over when exposed to daylight. Talbot devised several ways of chemically stabilizing his results, making them sufficiently insensitive to further exposure that direct sunlight could be used to print the negative image produced in the camera onto another sheet of salted paper, creating a positive.

The "calotype", or "talbotype", was a "developing out" process, Talbot's improvement of his earlier photogenic drawing process by the use of a different silver salt (silver iodide instead of silver chloride) and a developing agent (gallic acid and silver nitrate) to bring out an invisibly slight "latent" image on the exposed paper. This reduced the required exposure time in the camera to only a minute or two for subjects in bright sunlight. The translucent calotype negative made it possible to produce as many positive prints as desired by simple contact printing, whereas the daguerreotype was an opaque direct positive that could only be reproduced by copying it with a camera. On the other hand, the calotype, despite waxing of the negative to make the image clearer, still was not pin-sharp like the metallic daguerreotype, because the paper fibres degraded the printed image. The simpler salted paper process was normally used when making prints from calotype negatives.

Talbot announced his calotype process in 1841, and in August he licensed Henry Collen, the miniature painter, as the first professional calotypist. The most celebrated practitioners of the process are Hill & Adamson. Another notable calotypist is Levett Landon Boscawen Ibbetson.

In 1842, Talbot received the Rumford Medal of the Royal Society for his photographic discoveries.

In 1852, Talbot discovered that gelatine treated with potassium dichromate, a sensitiser introduced by Mungo Ponton in 1839, is made less soluble by exposure to light. This later provided the basis for the important carbon printing process and related technologies. Dichromated gelatine is still used for some laser holography.

Talbot's later photographic work was concentrated on photomechanical reproduction methods. In addition to making the mass reproduction of photographic images more practical and much less expensive, rendering a photograph into ink on paper, known to be permanent on a scale of hundreds if not thousands of years, was clearly one sure way to avoid the problems with fading that had soon become apparent in early types of silver image paper prints. Talbot created the photoglyphic (or "photoglyptic") engraving process, later perfected by others as the photogravure process.