In 1830, it took eight hours to take a photograph. In the case of portraits, the subject had to stay very still for a very long time for the image to be recorded clearly. Today, with smartphones capturing every fleeting moment, saying "cheese" has become less of an ordeal.

On this date, August 19, in 1839,the French government made the daguerreotype technology available to the public. Developed by  Louis Daguerre and Joseph Nicéphore Niépce, it produced images using copper plates coated with iodised silver. World Photography Day commemorates this breakthrough. To celebrate 175 years of photography, here's a clip that traces the evolution of the form.