Exhibition of the week Michelangelo and Sebastiano

National Gallery, London WC2 (020-7747 2885, www.nationalgallery.org.uk). Until 25 June

“You probably haven’t heard of Sebastiano del Piombo,” said Olivia Mcewan in City AM. Born in Venice in 1485, he was an artist mostly notable for his links to the “Renaissance superstar” Michelangelo. The latter was ten years Sebastiano’s senior, and at the time they met was completing work on his masterpiece, the ceiling of the Sistine Chapel. The two men went on to collaborate artistically and “shared a friendship that lasted 25 years”, with Michelangelo acting as a mentor to the younger man. Now, a “rigorously academic” new show at the National Gallery tracks the “twists and turns” of their partnership, bringing together an impressive selection of their paintings, drawings and sculptures. What’s more, it features a wealth of “intimate” letters exchanged between them, which create a “vivid impression” of 16th century Rome’s “unforgivingly competitive art scene”. It adds up to an “utterly fascinating” experience.

Relatively little is known about Sebastiano, and it’s unclear why the “notoriously grumpy” Michelangelo was so helpful to him, said Waldemar Januszczak in The Sunday Times. One theory has it that the “scheming” master befriended him to frustrate his “great rival”, Raphael. By promoting Sebastiano, Michelangelo hoped to deny Raphael influence and patronage. In any case, he promoted Sebastiano, employed him and gave him drawings to work from. An early highlight of their collaboration is Sebastiano’s “innovative” 1512 painting Lamentation over the Dead Christ, for which Michelangelo supplied the initial sketches. The work depicts Christ stretched out on the ground at Mary’s feet, while a “ghostly” moon casts “eerie” light on the scene. However, on the evidence here, Sebastiano never really delivered on this promise. Furthermore, many of the works attributed to him here are in such poor condition that they tell us little about this most “elusive” artist of the Italian Renaissance.

The show feels “thin”, said Laura Cumming in The Observer. Not only is Sebastiano “somewhat stinted” – many of his “finest” paintings are missing – but there are little more than a handful of works by Michelangelo. These include two “vast” marble figures of the risen Christ and the Taddei Tondo, the only Michelangelo marble in Britain. Elsewhere, we see a plaster copy of his “devastatingly strange” but untransportable Pietà from St Peter’s in Rome, and the “tremendous” drawing Risen Christ. Ultimately, though, this “small selection” of masterpieces will only make you “long” for “a full-scale Michelangelo retrospective”.