Art of Light: German renaissance stained glass, National Gallery, London

A great deal has been written about the relationship between artists and light. Painting with light. Luminosity. Suffused with light. All those phrases are over-familiar to anyone who has read or thought anything whatsoever about Impressionism and its many aftermaths.

Very seldom does stained glass get referred to in this context, in spite of the fact that the art of stained glass in our churches, which flourished in Europe from about the 12th century onwards, is all about the way in which a material works in conjunction with natural light. Stained glass goes hand in hand with light. Light makes it happen. Light illuminates the scene.

The art of stained glass in Europe reached a particular pinnacle in Germany at the turn of the 16th century, and this show in the Sunley Room of the National Gallery, modest in size, immodest in achievement, gives us examples of some of the best of what little has happened to survive.

The show begins by demonstrating what a hands-on business glass-making has never ceased to be. A vitrine contains some of the tools you would have needed to create the glass. Making it sounds a simple enough matter. You draw up a design, and spread it out on a table top. You lay pieces of glass down on top of that design to give you some idea of the basic shapes you're after. You cut each piece to fit. You score the pieces of glass with an iron rod. You snap it with pliers. After you've got the individual pieces, you paint them, or stain them. Then, having heated up your soldering iron, you fix all the bitstogether with lead strips. It sounds labour-intensive. It also sounds a bit like painting by numbers.

By the beginning of the 16th century in Germany, some of the greatest artists Albrecht Drer and Hans Baldung, for example were involved with the design of glass. And the glass itself was reaching new heights of sophistication. New, illusionistic effects were being achieved, the likes of which had not been seen before.

Look at a piece such as Tobias and Sarah on Their Wedding Night, which was made in about 1520. It's a chaste scene. The couple are asleep in their bed, heads gently leaning together. The bed itself is overlayed with a tapestry-like covering in a most marvellously vibrant, almost yelping, blue.

There are marvellous effects everywhere in this piece: the folds of the ruby-rich curtains that hang around the bed; the decorative detailing on that bed cover, which seems to incline towards the heraldic; the small dog, snugly curled up at the bed's foot inside his own tiny roundel of glass. It is a marvel of comparing and contrasting colours, of carefully judged perspective, of crisp detailing.

And then there is light itself. Some of these pieces seem to have scooped up light in fat dollops, like so much molten gold in a crucible. Look at a tiny glass roundel called The Virgin as Queen of Heaven, which is based on a design by Drer, and dates from around 1530. It seems to be literally drinking in the sunlight.

To 17 February (020-7747 2885)