In the 1700s, Britons Thomas Wedgwood and Sir Humphry David used paper coated with silver chloride to produce images of paintings and profiles. when exposed to light the whole paper turned black. In 1827, a French physicist named Joseph Nicèphore Nièpce made the earliest photographs on record, called heliographs.
Around 1831, French painter Louis Jacques Mandè Daguerre used silver plates coated with light-sensitive silver iodide to make photographs. He used mercury vapors to develop the image. These pictures were not permanent but gradually darkened. British inventor William Henry Fox Talbot developed a fixing process to keep the images from darkening: coating the developed plate with a strong ordinary salt solution. Daguerre was the first to use this method and perfected the process of making unreproducible images on silver plates.
Talbot also invented the paper negative which allowed an unlimited number of prints to be made. His method, called the calotype process, required 30 second exposures in order to make a good image on the negative. And the grain structure of the paper negative appeared in the final picture.
In 1847, a glass-plate negative method was invented by French physicist Claude Fèlix Abel Nièpce de Saint-Victor. This method used albumin as a coating material. It made an image with great definition but needed long exposures. Frederick Scott Archer started using wet glass plates with collodion instead of albumin in 1851. This type of negative had to be exposed and developed while wet, so photographers needed a darkroom nearby. Using horse-drawn darkrooms, American photographer Matthew B. Brady and his staff took thousands of collodion photos on the battlefields of the Civil War.
As early as 1874, British merchant Richard Kennett began using dry-plate negatives which could be exposed dry and not be developed right away. In 1878 another Briton, Charles Bennett, started making dry plates coated with gelatin and silver bromide, much like those used today.
In 1883, American George Eastman made film out of long strips of paper. In 1889, he made the first transparent, flexible film support out of ribbons of cellulose nitrate, inventing roll film. This marked the beginning of a new era of film in which amateur photography was possible.