I've also been told by an older priest that a pope "has to SAY he's teaching ex cathedra" in order for the teaching to BE ex cathedra.   This is not true:   Vatican I never said that. 

Anytime a pope solemnly teaches definitively -- whether in a bull, encyclical, by promulgating the texts of an ecumenical council, or by any other method or venue-- on a point of faith or morals to the *entire Church*, such a teaching is ex cathedra.   

Where many "traditionalists" do err is by extending infallibility beyond this.  

It's important to emphasize:
-Aquinas made mistakes
-Saints made mistakes 
-Doctors made mistakes
-Popes made mistakes in fallible capacities
-Sacred Congregations made mistakes 
-The common teaching of theologians in a given era can & have been mistaken
-Most of these mistakes were made in good faith
-If a person obstinately denies a dogma, he's no longer Catholic 
-Infallibility is given to Peter alone under certain conditions