Final answer:
The term for how closely a film adaptation sticks to its source material is known as its fidelity, which involves retaining the essence of the text in terms of themes, characters, and narrative.
Step-by-step explanation:
The degree to which a film adaptation adheres to its original source material is often described as its fidelity. In terms of cinematic adaptations, when a critic notes that a director has captured the 'essence' of a text, it suggests that the filmmaker has successfully retained the core themes, characters, and narrative of the source material. However, complete fidelity is rare due to the intrinsic differences between film and written formats. The film adaptation may change or omit certain elements to better suit the visual and time constraints of cinema. When analyzing such adaptations, one looks at how the director has managed these transformations and whether they have effectively conveyed the source material's message and tone. For example, a thesis asserting that director Joseph Papp captured the essence of a play implies that Papp's film adaptation retained the play's original spirit and intent.