He altered the course of Western art with a completely new approach to light and form, yet barely 50 works created by Caravaggio during his 38 years have survived. Now scholars claim that one more, a previously unknown painting, has been discovered in a private collection in Britain.

The oil on canvas depiction of Saint Augustine, an expressive, mature work dated to around 1600 – when he was 28 – is to appear in print for the first time in a book on Caravaggio produced by Yale University Press.

A leading scholar, Sebastian Schütze, professor of art history at the University of Vienna and one of the book's co-authors, called the work a significant discovery.

He said: "It has never been published. What looked like an anonymous 17th-century painting revealed its artistic qualities after restoration."

The painting fits in to Caravaggio's oeuvre around 1600, when his style was sculptural and monumental, with powerful movement and emotional expression.

Overlooked in a private collection, where it was considered the work of an anonymous hand, documentary evidence has now been unearthed to support the attribution.

Although covered in old varnishes and repaints, its potential was spotted by Clovis Whitfield, a British art historian and dealer with a track record in discovery.

The painting can be traced to one of Caravaggio's most powerful patrons in Rome, Vincenzo Giustiniani. A Saint Augustine of similar dimensions – 120cm by 99 cm – is recorded in his 1638 inventory.

Michelangelo Merisi da Caravaggio (1571-1610) was a revolutionary among artists, revered by masters through the centuries for his radical use of light and dark – chiaroscuro – and the theatrical biblical narratives he painted directly from posed models.

One of the west's most innovative artists, his use of light was as innovative as the Renaissance development of perspective.

But his was a tempestuous life blighted by violence, brawls and trouble with the authorities. He killed a man, either over a woman or a tennis match, and died in mysterious circumstances, although scientists last year used carbon dating and DNA checks on his likely remains, excavated in Tuscany, and found extreme levels of lead poisoning, possibly from the lead in his paints.

Another leading Renaissance scholar, David Franklin, director of the Cleveland Museum of Art and co-author of the book, said the Saint Augustine discovery was important because it is totally new.

He said: "Even the composition had not been recorded in other copies. Often a [lost original] composition is known from copies but not this one."

He added: "What's interesting is that it's a rather conservative image. Maybe that's why it hadn't been known.

"It shows a side of Caravaggio perhaps that is not as drastic and antagonistic as usual but where he was working very closely with Giustiniani to try to create a much more quiet image of a saint."

He described the Giustiniani provenance as "compelling". The painting remained in the Giustiniani collection until sold in the mid 19th century.

It will appear in Caravaggio and His Followers in Rome, to be published next month by Yale University Press in association with the National Gallery of Canada.