Principles of the pinhole camera have been known since antiquity, Aristotle (384 to 322 BCE) understood the optical principle of the camera obscura.
Leonardo da Vinci described camera obscura in his notebook.
Camera obscura is used as an aid to drawing.
The German chemist professor at the University of Altdorf Johann Heindrich Schulze discovered that certain silver salts, most notably silver chloride and silver nitrate, darken in the presence of light.
French author Tiphaigne de la Roche anticipated photography in his book Giphantie.
Sweedish chemist Carl Wilhelm Scheele discovered that ammonia removed unexposed silver nitrate and did not affect the blackened metalic silver.
Thomas Wedgwood published a paper about method of chemically staining an object’s silhouette to paper by coating the paper with silver nitrate and exposing the paper, with the object on top, to natural light, then preserving it in a dark room (he do not know the method how to preserve the image).
English chemist and physicist William Hyde Wollaston patented camera lucida, another optical device used as a drawing aid by artists. William Fox Talbot used a camera lucida and it was a disappointment with his resulting efforts which encouraged him to seek a means to "cause these natural images to imprint themselves durably".