Self-portrait of Antoine Francois Jean Claudet (1797-1867) and his son Henri Posed with Claudet's Invention, The Focimeter, in 1856. The Focimeter helped photographers achieve perfect focus on the daguerreotype plate when using achromatic lenses. Claudet was a student of Louis Daguerre, inventor of the daguerreotype; along with the focimeter, he developed other technical instruments to improve the taking of photographs, and was honored by Queen Victoria and Napoleon III of France.