Gorsky was a member of the Royal Photographic Society between 1920 and 1932.. Perhaps Prokudin-Gorsky's best-known work during his lifetime was his color portrait of Leo Tolstoy, which was reproduced in various publications, on postcards, and as larger prints for framing. The fame from this photo and his earlier photos of Russia's nature and monuments earned him invitations to show his work to the Russian Grand Duke Michael Alexandrovich and Dowager Empress Maria Feodorovna in 1908, and to Tsar Nicholas II and his family in 1909. The Tsar enjoyed the demonstration, and, with his blessing, Prokudin-Gorsky got the permission and funding to document Russia in color. In the course of ten years, he was to make a collection of 10,000 photos. Prokudin-Gorsky considered the project his life's work and continued his photographic journeys through Russia until after the October Revolution. He was appointed to a new professorship under the new regime, but he left the country in August 1918. He still pursued scientific work in color photography, published papers in English photography journals and, together with his colleague S. O. Maksimovich, obtained patents in Germany, England, France and Italy. In 1920, Prokudin-Gorsky remarried and had a daughter with his assistant Maria Fedorovna née Schedrimo. The family finally settled in Paris in 1922, reuniting with his first wife and children. Prokudin-Gorsky set up a photo studio there together with his three adult children, naming it after his fourth child, Elka. In the 1930s, the elderly Prokudin-Gorsky continued with lectures showing his photographs of Russia to young Russians in France, but stopped commercial work and left the studio to his children, who named it Gorsky Frères. He died in Paris on September 27, 1944, a month after the Liberation of Paris. He is buried in the Sainte-Geneviève-des-Bois Russian Cemetery. The method of color photography used by Prokudin-Gorsky was first suggested by James Clerk Maxwell in 1855 and demonstrated in 1861, but good results were not possible with the photographic materials available at that time. In imitation of the way a normal human eye senses color, the visible spectrum of colors was divided into three channels of information by capturing it in the form of three black-and-white photographs, one taken through a red filter, one through a green filter, and one through a blue filter.