In northern Italy in the middle of the 15th century, a teenage boy was painting pictures unlike any that had been seen before. Andrea Mantegna, a carpenter's son from Padua with an insatiable appetite for classical art and a massive chip on his shoulder, strove to create a vision of the ancient world that would feel unprecedentedly real and immediate, while making himself rich and famous in the process. To church walls, he added startling frescoes with novel perspectives, from which figures loom ominously over the viewer.
At the same time, in Venice, a very different character was also aspiring, in his own quiet way, to turn artistic tradition on its head. Giovanni Bellini was a profoundly private man who barely left his parish. At first sight, it's hard to imagine that these two greats of the early renaissance would have had much to say to one another. Where Mantegna's art is anguished and attitudinous – his haggard, quasi-sculptural forms can look as though they've been gouged out of slate – Bellini's is serene, bathed in a cool but transporting light that symbolises divine grace.
Indeed, the two artists came to epitomise opposing principles: Mantegna belongs to the central Italian tradition which would go on to produce Michelangelo, Leonardo and Raphael, artists who mapped the contours of the human body through rigorous drawing; Bellini, on the other hand, was the father of the more sensual Venetian tradition, which reached its apotheosis under his pupils Titian and Giorgione.
Chalk and cheese, surely? Yet a forthcoming exhibition at the National Gallery, called, simply, Mantegna and Bellini, places the two artists side by side to reveal the unlikely things that unite them – not least the fact that they were brothers-in-law.
"They were very different artists, completely opposed in their aesthetic interests," says the exhibition's curator, Caroline Campbell. "Yet if you look beneath the surface of their paintings, you can see that each was very aware of what the other was doing."
The two men lived at a time when the "modern" conception of the artist was still being forged, the medieval role of the anonymous craftsman-artist giving way to a more self-conscious and some might say, self-important, idea of what it means to create art. "They were each trying to find out who they were as artists," says Campbell, "and looking towards each other with a sense of competition."
Born around 1431, Mantegna, "came from nothing," as Campbell puts it - his first job was tending goats - but once established as an artist, his rise was unstoppable. Immersed in classical culture from an early age by his teacher, the antiquarian and painter Francesco Squarcione, he studied ancient Roman architecture and took part in archaeological digs. In his early works, such as the frescoes of the life of St James in the Church of the Eremitani in Padua (sadly destroyed in the Second World War), he played with perspective and extreme foreshortening to whip up drama. Repeatedly, he faced the charge that his hard-edged forms resembled painted sculpture rather than painted reality, an accusation made by Squarcione himself, with whom – not untypically – Mantegna ended up at loggerheads.
Bellini was more comfortable in his social status. A member of Venice's "citizen" class, second only to the aristocracy, and a scion of the city's leading artistic dynasty, he was embedded in a system in which family workshops vied for lucrative commissions from the state and Venice's powerful religious fraternities. While his father Jacopo and elder brother Gentile both excelled in the city's time-honoured genres (Gentile's paintings remain some of the most popular images of Venice), Bellini seems to have been determined from an early age to transcend Venice's provincial and essentially medieval traditions. His "sacred conversations", for example – images of the Virgin with saints, still found throughout the city – combine the characteristic Venetian feel for colour with a new, monumental – even Mantegna-esque – approach.
The two men actually met after Jacopo Bellini became aware of Mantegna's growing renown and sought him out with the intention of marrying him to his daughter – Giovanni's half-sister – Nicolosia. "Marriage then was first and foremost a business transaction," says Campbell. "Jacopo had two brilliant artist-sons. To add a third, arguably even greater talent in the form of Mantegna would have made the family studio a formidable force." Mantegna seems to have seen the wisdom of this arrangement – certainly at first. (What Nicolosia felt, history doesn't record.)
The National Gallery exhibition argues that Bellini "found himself" as an artist by looking at Mantegna. While a lack of documentary evidence makes it difficult to chart this in detail, Mantegna's impact on Bellini's hitherto placid, gothic-tinged art can be seen in a comparison of their respective interpretations of the Agony in the Garden, Christ's vigil, prior to his arrest and crucifixion.
The mood of tragic exaltation in Mantegna's version, compounded by the swirling chiselled forms of the rocky landscape on which Christ kneels before the holy spirit, is carried through into Bellini's painting, although, as Campbell points out, Bellini's figures "interact more naturalistically with the landscape".
This ability to make his figures appear as though they exist in real landscapes, rather than on rustic stage-sets (as they arguably do in Mantegna's work), is perhaps Bellini's greatest contribution to art. He also achieves a richer and more realistic sense of light and colour: in his picture, the pink of the dawn sky is reflected in the orange sand around Christ's feet.
While Bellini was establishing himself as the great teacher-figure of Venetian art - just about every significant Venetian artist of the succeeding generation passed through his studio - Mantegna accepted the position of court painter to the Gonzaga family, dukes of Mantua. Ensconced in one of the most refined and luxurious courts in Europe, well remunerated and with the freedom to paint pretty much what he wanted, Mantegna no longer needed the Bellini clan.
Yet he appears to have been looking back at what his brother-in-law was doing in Venice: Mantegna's late work is infused with a Bellini-esque treatment of light and landscape, such as Minerva Expelling the Vices from the Garden of Virtue (1500-2), in which the fanciful mythological action feels like it is taking place in a credible, temperate, northern Italian landscape, with damp grass and cool, rather overcast, light.
Mantegna and Bellini are artists who exist just beyond the reach of biography, too remote in history to come fully into focus as individuals. Yet looking at each man's art we feel we can get a sense of the person who created it. Mantegna comes across as a turbulent, even tormented maverick, while after looking at Bellini's coolly spiritual paintings it's hard to imagine that the person who created them was not a "nice man". Is this an example of art's ability to speak to us across time? Or are we simply deluding ourselves that we can get inside the heads of such people?
"That's the million-dollar question behind art history," says Campbell. "Mantegna feels quite needy. He's got this drive to push himself, and he's very litigious, keen to protect his intellectual property, so we have the documentation of the various court cases. He can be very courteous, and also very difficult. But in the end he gets the worldly success he craves, becoming a gentleman with his own coat of arms."
By contrast, she says, "we know so little about what Bellini thought and felt that you come to the conclusion he wanted it that way. The art itself is also quite private. It takes quite a lot of looking before it fully reveals itself to you."
But the real elephant in the room with Mantegna and Bellini, as with all artists of this period, is whether they're absolutely great in their own right or simply precursors of the geniuses of the following century. Even if we don't happen to like the work of Michelangelo and Leonardo, we've got it hard-wired into us that the Sistine Chapel and the Mona Lisa represent art's great climax, while the artists who came before are just, well, the guys who came before.
"That's a view that's been around 500 years," says Campbell. "But now I think we need to shake up our ideas of the renaissance. Mantegna and Bellini are among the greatest-ever European painters. They don't deserve to be viewed as precursors to anything. Their work stands on its own."
Mantegna and Bellini opens at the National Gallery, London WC2 on October 1. See: nationalgallery.org.uk