Experts are surfacing to dispute the authenticity of a photo from 1840 purported to be of Constanze Mozart. “There are no outdoor photographs of groups of people dating from 1840, because the lenses invented by Joseph Petzval, which were to make such portraits possible, were not available yet. It was simply not possible in 1840 to take sharp outdoor pictures of people as long as the necessary exposure time still amounted to about three minutes.”