Before he was plastered on T-shirts around the world, before he was a household name, before he led a revolution, a med school student named Ernesto Guevara de la Serna went on a road trip. The ambitious route through the Andes, into the Amazon, and finally to a leper colony, where Guevara and his friend Alberto Granado wanted to work, was taken on a small motorcycle lovingly nicknamed the Mighty One. Walter Salles’ moving new film, “The Motorcycle Diaries,” chronicles their entire journey with a subtlety that is unique in contemporary cinema.

Interestingly, Guevara remains an enigma: Salles chooses to focus not on the hero’s inner workings but the landscape of his adventure. He wisely allows the experience of 1950s South America to work its magic on the audience in the same way that it may have on Che himself.

The film is made up of a series of episodes which move from the frivolous to the profound. When visiting his wealthy girlfriend Chichina (Mia Maestro), Guevara (Gael Garcia Bernal) typifies a young intellectual out for a good time, unaffected by anything but love. After promising himself to her with deep feeling, while at the same time frustrated that she refuses to sleep with him, Guevara leaves with Granado (Rodrigo de la Serna) for the wild mountains.

There, the two friends are exposed to many of the local inhabitants, due to their need for shelter and repeated bike problems. Some of them are dirt poor like the indigenous people around Cuzco that treat the two friends with kindness. While Granado seems to resist the sadness of their state, Guevara retreats into himself, greatly troubled by their plight. By the time they reach the leper colony, Che channels the intensity -that carries him across the continent into the dream of a united South America.

By working with lepers, local farmers and indigenous people as his actors and filming entirely on location, Salles does more than just show off the wonders of Peru, he makes a solid case for Guevara’s argument. The hard-edged valleys and snow-covered overpasses of the Andes whisper of life’s cruel beauty. The South Americans on the other hand, speak for themselves; their similarly weathered and worn faces fill the camera.

Every chance he gets, Salles finds intensity through movement. Instead of simply showing a river boat in the water at night, he uses time-lapse photography to drift around it, catching the light dancing off the water. Throughout it all, the film is bathed in grain, stirring up a sense of nostalgia while at the same time flickering with the movement of progress. As in “Y Tu Mama Tambien,” the comedic scenes of “The Motorcycle Diaries” have a secret suffering within them. This pain gradually accumulates until it isn’t hidden anymore. By the time Ernesto attempts to explain his journey to a homeless couple — “We travel just to travel,” he says — the words are hollow and he knows it.

Although the film becomes less interesting when it loses its subtlety, as when Guevara defies the Amazon river by swimming across it, its beautiful photography and natural acting carry the picture home. And as a final surprise, Salles caps the film with moving photographs of each person along the journey looking straight into the camera, out to us, the new travelers. In these final black and white shots, it isn’t a stretch to imagine Salles’ beautiful shot of Machu Picchu reflected in each face.