Stanislas Ratel and Charles Choiselat were friends, neighbors in the St. Sulpice quarter in Paris, devout members of the same Catholic congregation, partners in daguerreotypy beginning around 1840, and, brothers-in-law after Ratel’s marriage in 1850 to Marie Ange Zoë Choiselat. Picturing Ratel seated at a desk splayed with open books and with quill pen in hand, the portrait may have served to memorialize his graduation, as he received his engineering diploma the same year. Ratel went on to a career as a civil engineer for the Paris-Orleans Railway. Choiselat was a skilled chemist who published improvements to the daguerreotype process.