lenses for large sheet film cameras are especially difficult to design. cameras and their lenses have been made since the 19th century. some from before world war ii, are still usable today. computers now let engineers make better lenses, though, because they can calculate the way that light goes through the lens and find the best design for each task. together with lenses, filters, macro lenses, teleconverters, wide-angle and tele attachments are used.