The poem looks at the human face and asks what it really shows. The speaker says a face can reveal what's going on in a person's mind, or it can hide it. Either way, it isn't a trick. The phrase "no computer trick" sets the face against anything digital or edited: what we see is natural, the result of a life actually lived.
The second half moves toward aging. Wrinkles and spots appear slowly, and the speaker treats them as a gradual unveiling rather than a loss. The pairing "vision and revision" suggests that how we see a person keeps changing, and that the face itself is constantly being reworked by time. By the end, "a total image" suggests the face holds everything together: thought, experience, and years.
The tone is calm and thoughtful. The speaker seems to accept aging without complaint, even to value it as honest. The mood is quiet, reflective, and gently admiring of what an ordinary, unretouched face can tell us.