A masterpiece in your front room

How should an artwork be analysed? What is more important - historical background or brush strokes?

Let us scrutinise an evocation of a Sunday spent on the banks of the Seine in 1884. We see a top-hatted gentleman looking out at the river. A lady with a parasol holds on to his arm, and has a monkey on a lead. Other people lounge on the grass. Three dogs romp. A child plays. A young woman fishes by the water's edge. The vision is Georges Seurat's A Sunday on La Grande Jatte.

What is arresting is the very different way in which the picture is seen now, compared to how it must have struck its first viewers. Today the painting comes across as a beautifully arranged, if rather static, portrayal of the Parisian bourgeoisie in the local park. On a different river, they might have been in Battersea. Viewers in the mid-1880s, however, probably found the painting as daring in its subject matter as in its style of painting (pointillism). For the picture has strong hints of the demi-monde, of decadence among the pretty parasols. The monkey indicates that the lady holding his lead was a mistress at least - singesse (female monkey) then being a slang word for prostitute. John House, a professor at the Courtauld Institute of Art in London, is certain that people who saw it would have picked up the allusion. Indeed, the young lady fishing may have been after a different kind of catch. It's another pun: the French pecher, to fish, being very close to pecher, to sin. And after all, Guy de Maupassant once complained of the islands of the Seine that there were so many people making love on the banks that it was impossible to find a place to do it himself.

One privilege of editing the television series Private Life of a Masterpiece, which returned to BBC2 this month, is to be exposed to the intriguing ways in which the meaning of art changes. This has been part of the discourse of modernism in art for the past hundred years. Marcel Duchamp said: "It is the spectator who creates the museum," meaning that the way we look at a painting or sculpture is a central part of its meaning. Mick Gold's film on Degas's The Little Dancer Aged 14, part of last year's Private Life series, set out the same insight. When Degas exhibited the sculpture in 1881, critics were outraged. One wrote: "With animal effrontery she thrusts her little muzzle into the world." He was offended because, at that time, ballet dancers were not the daughters of the middle class, but working-class girls who often resorted to prostitution. The model for the sculpture, Marie van Goethem, was probably prostituted by her mother and ended up on the streets when her tutu days were over. Yet this is the sculpture admired by many of today's gallery-goers as a pretty and touching evocation of a young girl doing a ballet step.

Another pleasure of making the series is that it may help to rescue iconic artworks from the awful condescension of fame. With 50 minutes in which to examine one artwork, a programme can reveal anew just how complex and clever and rich it is. Even the most cliched paintings emerge fresh. How many who see Van Gogh's Sunflowers at the National Gallery in London know the religious richness of his work? He portrayed 12 sunflowers to symbolise Christ's disciples and added two or three more to balance the painting.

Yet what seems to appeal most of all is the detailed exploration of just what the artist was doing with paint, wax or stone. In the second programme of the current series (9 April), there was a moment of genuine revelation when J0rgen Wadum of the Mauritshuis museum in The Hague demonstrated that Vermeer got his proportions and perspective right in The Art of Painting not so much with a camera obscura but by deploying a pin, a piece of string and some chalk. The pinhole is visible to this day. There may have been another such moment in the programme on The Battle of San Romano (16 April), when Martin Kemp explained that Uccello used a "ghost pavement", a grid of lines, to make his revolutionary advances in perspective. People in Uccello's time must have said "Ah!" remarked Kemp. They are still saying "Ah!" today.

By the same token, an enduring delight of The Night Watch (featured in last year's series) is the forward movement of the guardsmen, led by Captain Frans Banning Cocq and Lieutenant Willem van Ruytenburch. The painting seems like a still from a movie. How did Rembrandt do it? One of several devices was the way he painted the partisan, or spear, in van Ruytenburch's left hand so that it appears to project from the flat canvas. John Bush's film looked at the X-ray of the painting and found that Rembrandt had altered the partisan blade several times, foreshortening it to achieve the perfect illusion of 3D.

Where I think the format of Private Life of a Masterpiece has an advantage over some arts television is in essaying the biography of a single artwork. It is possible to draw together all the factors that influenced its creation - the painting traditions the artist drew on or revolted against, his own personality, the sexual and art politics of the time, his own preparatory work. In this way, the Private Life approach combines John Berger's emphasis on the importance of social context with the aesthetic focus of the late Peter Fuller, editor of Modern Painters, who stressed that what matters is the paint, what is painted and how it is painted.

Some art historians, many painters and doubtless the shade of Peter Fuller may consider that Private Life gives too much emphasis to the painter's life. Attempting to get the balance right in the very first (2001) edition of the series devoted to Michelangelo's David, we had a Post-it note stuck up in the editing suite saying "The banned word in this programme is . . . Michelangelo."

Yet our final film in the present series, which looks at Gustav Klimt's Kiss, gives the lie to the notion that the biography of the painter is of no import. In the programme, Klimt himself says: "Whoever wants to know something about me ought to look carefully at my pictures and try to see in them what I am and what I want to do." The psyche of this remarkable man, almost as skilled in seduction as he was in draughtsmanship and painting, permeates most of his work. You might not guess that Klimt had 14 paternity suits levelled against his estate when he died, but you can tell that this was a man with a passion for women and one who took delight in their bodies.

The purists have their point, however: look hard at the canvas and there is everything most valuable. Again, the joy of having time to do this is incomparable. And television has certain privileges. It's now not possible to see all three panels of The Battle of San Romano together, scattered as they are across Europe in three different galleries. Television can unite them. We can show tiny details, linger undisturbed by tour parties, track smoothly along a canvas, see it glowing in the dark. Indeed, the Uffizi panel of The Battle is poorly displayed in a room with huge sunny windows. You'll never get to see the painting looking as good as it does in Ian Michael Jones's programme. One of the art historian contributors bitterly regretted not being able to come to the Uffizi when we had our filming lights set up. Only then was it revealed in all its glory.

Jeremy Bugler is the series editor of Private Life of a Masterpiece, which continues on Saturday nights at 8.10pm, BBC2