Geoffrey Crawley was a photographic scientist who debunked theCottingley Fairies and formulated this FX37 developer; other things also happened, but for the purpose of this description, we’ll leave it at that. FX37 is designed to provide maximum acutance on t-grain films like Kodak TMax and Ilford Delta, but it can also be used to good effect with more traditional black and white film. This kit mixes enough chemistry for up to 8 rolls of film.