sentences:  It was the first autofocus (AF) 35 mm SLR camera to reach production.It had a built-in through-the-lens (TTL) electronic contrast detection system to automatically determine proper subject focus and drive a lens to that focus point.Although it autofocused poorly and was a commercial failure, the pioneering ME F was a major milestone in the history of camera technology that pointed the way to all present day AF SLRs.