My son will be taking a photography class using b&w film at his college next semester and we're trying to figure out if his 420ex that he uses with the 5D I gave him at the start of the school year will be compatible with a film camera? He is looking at the EOS-1N or the Elan 7e or Elan IIe. As I understand it film e-ttl is the same as digital e-ttl. Is this correct? His budget is $100.00.