ASA/BS abbreviation for (Photography) an obsolete expression of the speed of a photographic film, replaced by the ISO rating [C20: from American Standards Association/British Standard]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014