ARTS: EXHIBITIONS: Pretentious? Lui?

ALEX KATZ'S paintings appear to be the work of a youngish man; but in fact he's a senior, indeed veteran artist, now in his 69th year. The pictures look young because they are stylish, interested in fashion, and painted with naivety as well as skill. They also show a lack of interest in maturity. Katz reached his signature style at the end of the 1950s, and since that time there has been no major development in his art, let alone a deepening of its thought. The exhibition at the Saatchi Gallery presents 25 years of Katz's painting. It's hard to say which are the earlier and which are the later works. They might all have been painted a quarter of a century ago, or they might have been painted yesterday.

This unchanging kind of picture makes Katz into an American classic, though not a classic of an elevated sort. You would have thought that, in a country in which fashion moves so rapidly, Katz's paintings - especially of the female form, which is his speciality - would soon look dated. They do not. His smart women with expensive clothes, scarlet lipstick, much mascara and dramatic hats have a kind of timeless Manhattan chic. Clothes and swimsuits are important. Katz can't paint the nude, and he has been wise to avoid the undraped figure. He would give himself away, for Katz is not really a figure painter at all. He is a painter of modern women in their get-up. Katz reminds me more than a little of the photographer Richard Avedon (his near-contemporary), another person who catches and crystallises style but cannot manage the nude. Katz, however, is more of an artist than Avedon.

For obvious reasons, Katz is connected with Pop Art. Katz became a celebrity at the same time as the Pop artists, and there are similarities of technique and subject-matter. Yet I cannot imagine him in an exhibition alongside Lichtenstein, Wesselman or even Rosenquist. He might seem more at home in the company of such older American realists as Fairfield Porter, George Tooker or Ben Shahu. The differences are that Katz shows no social conviction, avoids references to time and place, and paints on a far larger scale than they did. The bigness of Katz's paintings is a matter of both instinct and necessity. The feeling for size comes from the general expansion of American canvases after Abstract Expressionism. The need for a large picture is dictated by Katz's wrist and eye. He can't feel depth or model forms with tonal variation. Katz's brush does what he wants but is incapable of delicacy. He's a painter whose touch has to be dry and widespread. Little wonder that his major influence is the billboard.

No doubt this has endeared him to the Saatchi Gallery. The exhibition catalogue, much inclined to overpraise, talks about Katz while also mentioning Pollock, Courbet, Matisse, Piero della Francesca and other Renaissance mural painters. This is pretentious. Billboards were much more important to the growing artist. They combined glamour and the common touch. Furthermore, American advertisements in Katz's young days were simultaneously innocent and knowing. Nudes were not to be seen, though sexual attraction was a theme. Such adverts stressed youthfulness, and perhaps advertising in general is forever youthful. For surely there is no such thing as a mature advertisement? Katz's liking for painting people who are just emerging from adolescence into early manhood or (more often) womanhood is noticeable, and may be interpreted as part of the American dream.

Not a comment on that dream. Katz's paintings are free of opinions. Though they are works of art, you don't get much idea of the artist's aesthetic preferences. Human intercourse of various sorts is observed, but not assessed. The hand-in-hand people of Summer Triptych have been blanched of their emotions. In the beach parties recorded by Lincolnville, Labor Day or Round Hill, the leisured loungers have little to do with each other. Uneasy with multi-figure paintings, Katz often divides his compositions into diptychs or triptychs, or repeats motifs in the same picture. These are generally his weaker canvases.

The surprise of the show is the Katz's landscapes. They reveal more feeling for art than his figure works, yet it is certain that if Katz were exclusively a landscapist he would have no reputation at all. Or only the limited reputation of Neil Wolliver (born 1929; Katz was born in 1927), who for years has painted views of the Maine wilderness. Katz also lives in Maine when he's not in New York. I think there's a connection between these artists. Katz's landscapes are too contrived, but their very existence implies that he's a regional American painter of a decent old-fashioned sort.

Elsewhere in London, the Whitechapel Gallery presents the German artist Thomas Schutte. His exhibition has four elements. There are grotesque figures, both large and small; photographs of the heads of grotesque figures, which look as if they have been made from wax; some banal portrait drawings; and a series of spoof architectural models. These are his better works. Caricature in art has long since lost its interest. Sculpture that deals with architecture is a promising and relatively unexplored area.

! Alex Katz: Saatchi, NW8 (0171 624 8299), to 12 Apr. Thomas Schutte: Whitechapel, E1 (0171 522 7878), to 15 Mar.