After he retired on half-pay, Langlois devoted himself to painting. Studying with Girodet-Trioson, he specialized in landscapes, painting battles only, for he considered these to embody the most intense experiences life could offer. His paintings include the "Fire of Moscow", the "Battle of Eylau", the "Battle of the Nile", the "Battle of Montereau", the "Battle of Borodino", the "Battle of Wagram". He also used photography to document the Crimean War where he traveled with photographer Léon-Eugène Méhédin. He specialized in panoramic painting after having seen the "Panorama of Athens" by the first French panorama painter Pierre Prévost. Many of his panoramas were destroyed during the Siege of Paris (1870–1871).