In 13th century siver nitrate was discovered. In 15th century silver chloride was discovered. Diaphragm was discovered in 16th centuary.It was found that light darkens some chemicals(photochemical effect). First permanent photograph was made by a French inventer Nicephore Niepce. Later Louis Daguerre continued his work, expermenting with silver compounds and developed dauerreotype in 1837. The Government paid him royalty for his discovery and and gifted it to the world.