Ganja & Hess (1973)
Ganja & Hess is a 1973 horror film directed by Bill Gunn and stars Marlene Clark and Duane Jones. The film follows the exploits of archaeologist Dr. Hess Green (Jones) who becomes a vampire after being stabbed by his intelligent, but unstable, assistant (Gunn) with an ancient cursed dagger. Green falls in love with his assistant's widow, Ganja (Clark), who learns Green's dark secret.
More at Wikipedia.