Francisco de Zurbarán is one of the holy trinity of 17th-century Spanish painters, alongside Diego Velázquez and Bartolomé Esteban Murillo. That he is both the holiest and the least known to the public may be related. Many of his greatest devotional works are undeniably, even forbiddingly, austere, but they are also often touched with a graceful beauty. Never more so than in The Crucifixion of 1635, one of around a dozen he painted on that subject throughout his career, in which the eye is drawn away from the tenebrous depiction and theme by Christ’s loincloth: virginal white, exquisitely draped, a symbol of divine perfection amid suffering.

In the superbly curated major exhibition devoted to his work, which has opened at London’s National Gallery (it will then move to Paris and Chicago), the painting hangs alongside a later depiction of the same event, from 1655, Christ on the Cross with the Virgin, Mary Magdalene and St John. In this work, Christ is agonisingly closer to death, the light itself in the process of dying, while St John gazes from below, open-mouthed, and the Marys weep. There are many works of such devotion on view. The spellbinding Saint Francis in Meditation, bought by the National Gallery in 1853 to considerable opposition (in a letter to The Times, one MP described it as a ‘small, black, repulsive picture); the magnificent Agnus Dei, depicting a trussed lamb awaiting sacrifice, a symbol needing no explanation; above all, a reconstruction, uniting three paintings from Poznan and Grenoble, of the second-tier (of three) of the vast altarpiece from the Carthusian Monastery of Nuestra Señora de la Defensión in Jerez de la Frontera. In it, a work depicting a solemn Virgin with a mischievous looking Christ on her knee, adored by kneeling Carthusians, is flanked by an Adoration of the Magi to its left, and, to the right, a circumcision of a serene baby Jesus, in which the ritual’s practitioner appears to be enjoying his role a little too much. These works hint at another side to Zurbarán, as a gifted narrator, and as a master colourist. His depiction of cloth is remarkable, comparable to Veronese, perhaps owing to his keen observation of the finer products of his father’s trade.

He was born in 1598 in arid, mountainous, thinly populated Estremadura, the region from where many of the Conquistadors came. Unlike those desperate men, Zurbaràn was relatively privileged, and moved to and made his name in Seville, a city grown fabulously rich on the wealth of the Americas, and a beacon of absolutist Catholicism. His prodigious gifts were amply demonstrated in works such as an earlier crucifixion, that of 1627, with its muscular Christ that many thought a sculpture (Zurbaràn had trained as such). Seville’s governing council, on seeing such astounding efforts, exempted him from the usual qualifications required to be an artist in the city. His genius was evident.

From then on, the commissions flowed. Though synonymous with Seville, Zurbaràn was, along with Velazquez, commissioned to produce paintings on the theme of the Labours of Hercules for Philip IV’s new Buen Retiro Palace in Madrid. Two of them, Hercules and Cerberus and Hercules and the Cretan Bull – his only male nudes – are displayed in the exhibition. Their strange, elongated perspective, which entranced modern artists, is explained by their original positioning in the palace; visions of power to be viewed from far below.

The revelation of the exhibition though, at least for me, is the room of remarkable still lives, shared between Zurbaràn and his son, Juan, a gifted artist himself. The highlight is a loan from Pasadena, Still Life with Lemons, Oranges and a Rose of 1633. Zurbaràn clearly realised its greatness – it is the earliest signed and dated still-life from Seville – and used it to advertise his brilliance, recognised since in homages by Picasso, Cezanne and Dali, among others. Even then, in this apparently secular painting – relief, perhaps, for those less familiar with, or simply overwhelmed by, Catholic doctrine – the piety persists in this perfectly proportioned work; the cup of water on plate with a rose is a traditional symbol of the Virgin.

Juan, would die aged 29, probably in the plague of the 1640s that killed half the population of Seville. It changed the tone of his father’s work, which reverted to darkness, but of a bleaker kind, typified by that agonising crucifixion scene of 1655. Three years later, he left for Madrid. He died in 1664.

This exhibition succeeds magnificently in revealing the extent and diversity of Zurbaràn’s work. Even those paintings that have not survived are well-documented in commercial contracts. And yet. He left no self-portraits, but the exhibition’s final exhibit – another crucifixion – offers a tantalising puzzle. The Crucified Christ with a Painter, completed around 1650, in the wake of the death of Juan, has no precedent or comparison in western art, and is a deeply moving experience. Might the man with the pallet of paint looking with reverence upon the crucified Christ be Zurbaràn himself, returning to the subject that made his name and a reputation that continues to grow, as this fine gathering of his absorbing, mysterious oeuvre confirms?

Zurbaràn is at the National Gallery, London until 23 August.