This exhibition is classic Ed Ruscha: luridly painted mountain ranges; dates and numbers over loosely painted skies; images covered with painted words that might, if you work hard enough at it, bear some relation to the image they adorn, but mostly seem to bear no relation at all. And all executed in the style of a sign painting - rough and rudimentary, yet still evocative.

The title of Higher Standards, Lower Prices betrays Ruscha's early training in advertising.

It's a diptych of two almost identically painted mountain ranges, on the second of which the 70-year-old American paints a couple of rooftops (painted in a more basic style than the rest of the image to disrupt any passing notion of realism).

And, for an artist who was once at the cutting edge of the conceptual end of the Pop Art movement, the exhibition, perhaps surprisingly, also shows someone who clearly equates change with decline.

Azteca/In Decline, for instance, is another diptych showing a before and after image. A difficult painting to work out, it seems to show three brightly coloured awnings or building canopies, which have crumpled in a heap in the second painting.

Ruscha has often described himself as a deadpan painter, and this is very true. But here and there he betrays just a little personality to make us want to keep on looking.