For Prabhakara the self is not self-luminous, since it is not revealed in deep sleep. But every consciousness is self-consciousness [and is therefore self-luminous]. In every cognition the self is revealed as the subject of that cognition (cf. triputi-pratyaksa-vada) and never as its object. But cognition is passing; hence the self is not always revealed.
For Bhatta, as for N.V., self-knowledge is a later cognition; first comes object-consciousness. N.V. holds that the self is revealed through an introspection (anuvyavasaya) of the latter. Consciousness is never self-luminous but is inferred from the cognizedness of the object. Thus inferred, it reveals its subject as ego and we have a self-cognition in which the subject knows itself as the object of this cognition. "Against the majority of Indian thinkers who hold that the subject is never known as object, B. maintains that there is no contradiction in the self knowing himself as that object which is the subject of cognition." (Guidelines 223)