CHRISTOPHER SMITH "It boils down to the value of the shape and the colour." So wrote Terry Frost, the grand old man of abstract painting in Britain. Typically, he has even pared that sentence down to essentials.

CHRISTOPHER SMITH

"It boils down to the value of the shape and the colour." So wrote Terry Frost, the grand old man of abstract painting in Britain.

Typically, he has even pared that sentence down to essentials. It is perhaps easier to approach this stimulating show of his work in plural terms, that is, thinking of shapes and colours, and then enjoy constant interactions that are varied with endless subtlety.

At first glance Blue and Lemon, for instance, seems so simple as to be almost empty. But look again at that form, with something like a semi-circle of blue to the left facing one of yellow on the right. Then pause to compare each of the eight stripes of different colours in between that are all the more striking because they are separated by bands of white.

Spiral for Sun, another silkscreen print dating from last year, adds to colour – in this case bright yellow and deep orange made more vivid still by black – a sure sense of design. The whirling disc at the top is set off against a rising shape of interlocking half-moons. Here is a sense of space as well as great ingenuity.

Crisp and bright, colourful and presented both boldly and fastidiously, these pictures invite question and analysis, while yielding enough at every stage to give pleasure. This attractive demonstration of what John Piper called the discipline of abstraction runs atContemporary Arts until July 13.