。
I don't remember my father's face exactly.
Literal
I [topic-は] father [attributive-の] face [object-を] precisely [contrastive-には] remember-not-[state-ている].
正確に ('precisely, accurately') + contrastive は (正確には) gives 'precisely (at least)' — the nuance is 'I don't remember (precisely) — I might remember in general, but not precisely.' 覚えていない uses ている for the state of memory (or lack thereof). A bittersweet, honest admission.