I just got two 8x10 film holders and I'm looking to make a simple box camera. This means I need a cheap lens. I've been looking on Surplus Shed for cheap lenses but there's always the question of whether they cover a 8x10 or larger sheet of film. Overhead projector lenses seem like they would work for large- and ultra-large format lenses because they cover a sheet of paper. Has anyone ever tried one?