Ohio Genealogical Society (www.ogs.org) has a publication available of all Ohio photographers and all the years they were in business from 1839-1900.I have found it quite helpful. Gagel, Diane VanSkiver. Ohio Photographers 1839-1900. Carl Mautz Publishing, 1998. 115 pp. Hard cover. A directory of Ohio photographs is included with biographies of selected artists. A history of photography in Ohio adds much to this work.