Originally posted by IchabodCrane I've never heard of a formal independent test protocol to measure low light AF functionality
'Functionality' is a very general term. 'EV sensitivity' is more specific and measurable.
'Funtionality' brings in all the other settings and features of a camera. 'This camera AF is not functional unless it can do BIF in low-light', 'this camera is not functional unless I can track the eye of a model as she moves across a dark room'. Etc. 1,000,000 things to measure with 'functional'.
By now, after producing cameras with both AF and electronic metering for several decades, I would be surprised if there were no Japanese or other standards that set a framework for measuring both AF and metering EV sensitivity which all the camera makers used. Except Fuji