Millet has weighted his figures ponderously downward, the busy harvest scene is literally above them, and the high horizon line which the taller woman's cap just touches emphasizes their earth-bound role, suggesting that the sky is a barrier which presses down upon them, and not a source of release.
Millet is writing after the French Revolution of 1848 - after which a celebration of the "common man" became the cause celebre among artists. Prior to the French Revolution of 1789 most all paintings were portraits or beautiful landscapes commissioned by the wealthy and celebrating the world of literature, art, and wealth that adorned the walls of the upper class houses of Europe.
Millet's choice of peasants as subject matter suggests a certain dignity amongst his subjects but also a universality, a timelessness of the human condition embodied in the work. Their headgear, blue, red, and stained white, represents the tricolor of the French nation - and thus a brotherhood of man. The two characters to the left, animalian and formless as though crouching on all fours, are chained down to the earth, the physical, the daily grind and grunge of basic survival. There is no sense of the beautiful, the metaphysical, the ecstatic - nothing that makes the human condition human.
The nobility of the figures consists in the attempt, metaphorically speaking, to break through that horizon line, to stand up and enter into the realm of light, to break the eternal struggle of the land, the toil of merely surviving and ascend to something greater and more holy. The central figure wears a brightly colored arm sleeve. She seems to reckon, even in the midst of her poverty, that something beautiful must exist in this world.
Yet Millet's characters, for all their nobility, are unable to escape from that claustrophobic fatedness which weighs upon them. They are still dirt poor, fighting to survive, and bowed down by an intolerable situation which warps and changes them into something inhuman.
A direct contrast to this excellent painting can be seen in the painting "The Song of the Lark" (1884) by Jules Breton. Here the same subject matter, that of a peasant working in the fields, but there are distinct differences. First the subject is a young girl, not an old woman. She goes shoeless in the field but she goes to harvest (witness the scythe) and not to scavenge.
The time of day is morning as is evidenced by the rising sun, and not afternoon, as can be noticed in "Gleaners" by the angle of light and the fully reaped field.
Perhaps most significantly is that the main figure stands upright, breaking the line of the horizon, her head encircled by light of the rising sun, her mouth agape in wonder, and her eyes filled with amazement. She has just heard the sound of the early morning bird and stands transfixed, the sickle still in her hand, as the beauty transports her ecstatically out of her menial existence into another realm of beauty, thought, and wonder. Thus she is simultaneously in the benighted world of the earth, and in the illuminated world of the heavens.
Additionally, Breton's young subject stands in a posture reminiscent of Ancient Egyptian statues; left foot forward, right back and turned, hands rigidly at sides, head up and looking toward the golden panorama of the sky. Like the noblest figures of Egypt she too has taken on a godlike and timeless status - transported by the momentary realization of beauty which is akin to art.
As Millet was extolling the nobility of peasants (and by extension of all men) suffering under the chains of fate and weighed down by a glass ceiling of the sky, Breton indicates that escape from the muddy world of clay can and does occur. His character, transfixed by beauty, leaps into the heavens and thus becomes something akin to a god.