The Enlightenments, The Dean Gallery, Edinburgh

Devoted sisters see the light

You need the patience of a saint to sit through Tacita Dean's film The Presentation Sisters. With its longuers and silences, some may feel it's the aesthetic equivalent of watching paint dry. Others will see in its small acts of quiet devotion and ritual, which define these elderly Irish nuns' lives, a poetic evocation of the Sisters' spiritual existence.

The Presentation Sisters is a teaching order and the sisters spent their working lives in far-flung places such as Africa and Alaska. The film opens with the sound of bird song. Early morning sunlight plays on the gravestones of the convent's small cemetery:a reminder that the five women are approaching the end of their lives. Following the rhythm of their day, we witness the cycles of cooking, cleaning and praying, as they vacuum already spotless rooms, bake scones and make endless cups of tea. Dressed in neat blouses and skirts, with the same cropped grey hair and glasses, they have all come to resemble one another.

The predominant mode of the film is silence, which reverberates down the convent's polished halls. Dean lingers on empty rooms filled with heavy mahogany furniture like something out of a dark Victorian painting, and on beams of light flooding through stained glass windows into stairwells to create pools of mulberry-coloured light.

We see the sisters in a row at prayer in high-backed chairs, but more surprisingly find them enjoying a football match on TV. These are evidently worldly nuns, though even here their enthusiasm is decorous and muted. They joined the order when it was enclosed and when the garden inside the outer wall formed the perimeter to their physical world. Brides of Christ, they all wear wedding rings. Though they choose not to wear the veil, they are unable to recruit young novices in this secular age. Their life of devotion and ritual based around meals, domestic tasks and prayer is fast becoming an anachronism and it is this realisation that gives the film its poignancy.

Dean's work forms part of a group show at the Dean Gallery that comes under the Edinburgh Festival visual arts programme's umbrella title of The Enlightenments. Edinburgh epitomises the ideals of the 18th-century Scottish Enlightenment, and the theme offers contemporary observations on religion, philosophy, architecture and scepticism. This leads to a rather dry show, where the Turner prize-nominee Nathan Coley's painted tree trunks strain unconvincingly to question belief systems and investigate architectural structures inhabited by faith, while Joshua Mosley's digital film of animated clay figures, representing a fictional encounter between Rousseau and Pascal, seems like a version of The Magic Roundabout for philosophers.

But as well as The Presentation Sisters, there is a poignancy to Lee Mingwei's Letter Writing Project. Visitors are invited to take off their shoes and enter a Shinto-looking shrine to write letters to whomever they choose. These are left for visitors to read. Some of the confessions and outpourings are full of regret for the remembrance of things past and genuinely moving.

To 27 September (0131 624 6200)