I believe any photographs before 1850 would be extremely rare. This brief history of photography gives an idea of how far back we might expect to find a photograph of an ancestor. "The first camera was announced in 1839 by Jacques Daguerre. His popular daguerreotype process utilized copper plates, while the calotype process invented by William Fox Talbot recorded images on paper. The development of the collodion wet plate process by Frederick Scott Archer in 1850 cut exposure times dramatically, but required photographers to prepare and develop their glass plates on the spot, usually in a mobile darkroom. Despite their complexity, the wet-plate ambrotype and tintype processes were in widespread use in the latter half of the 19th century. Some cameras were fitted with multiple lenses for making cartes de visite." Source: Wikipedia, September, 2006