Johann Heinrich Schulze

Johann Heinrich Schulze (1687 to 1744) was a German professor and polymath who studied medicine, chemistry, philosophy and theology and became a professor of anatomy and several other subjects at Altdorf and Halle. He is best known for discovering that the darkening in sunlight of various substances mixed with silver nitrate is due to the light and not to the heat, as other experimenters believed, and for using the effect to capture shadows temporarily. In experiments of about 1717 he found that a slurry of chalk and nitric acid with some silver dissolved in it darkened in sunlight but not in the heat of a fire, and by putting stencils of words on a bottle of the mixture in the sun he produced copies of the text in dark characters. The impressions did not last, but his work laid a foundation for later efforts at photography, and many German sources credit him as its inventor on an extremely broad definition of the word.