Jasper Johns is one of the great “noodlers” of modern art. Noodling, a term that enjoyed currency at the time Mr. Johns first hit the scene in the 1950s, is about fussing and worrying images into existence, often with monotonous, obsessive repetitions. That the word has culinary connotations is appropriate because it is like kneading dough. Obviously, it is not a complimentary term in an era that venerates speed, decisiveness, and the verve of expressive gestures. But to an artist like Mr. Johns, intent on challenging and arresting such expectations, it is not altogether a putdown, either.

His proto-Pop, or as some called it at the time, neo-Dada painting and sculpture, was a calculated riposte to the excesses of Abstract Expressionism. At the same time, it was a bid to become its historically inevitable coda. Mr. Johns is an enigma, a nihilist who negates aesthetic experience of nonetheless protean productivity, both in terms of quantity and character. His art once insisted on its own nonchalance, with throwaway imagery, muted color sensibility, and busy but unexpressive paint-handling. Yet it always entails a labor intensity and self-regard that counterbalances the blase.

After an absence from the gallery scene (apart from the presentation of occasional work at Leo Castelli uptown, where he is a faithful), Mr. Johns’s new show at Matthew Marks is vaunted as his first New York show in eight years. And he is back with flying colors – or a lot of gray, at least. His MoMA retrospective in 1997 ended with paintings packed with arcane iconography: The monumental, untitled work from 1992-95 that graced the catalog cover threw together a ground plan of his grandfather’s house, trompe l’oeil devices, graffiti figures, imagery, lettering, and one of his amorphous “green angel” entities.

The new works recall both the austerity and monomania of the vintage Mr. Johns of flag, target, map, and lettering fame, but recaptures none of the seminal energy of his early years. He has a new motif-obsession, which gives its name to the title of the show: “Catenary.” Many works busy themselves with this curve. Truth be told, however, “catenary” is a fancy name for a mundane fact: The result of a cord held at two points, the curve is less “golden section” than limp washing line. The curves are literal presences in many of the canvases, which have appended slats of wood supporting the unmomentous string.

“Catenary (Manet-Degas)” (1999), for instance, has such a slat falling away from the right-hand side of the canvas, pinning the string to a hook near the bottom left edge. There may be transcriptions or homages to the illustrious Impressionists cited in the fussy, worried brushiness of the gray expanse underneath this straggling piece of string, but that is mostly the artist’s business. The title is stenciled along the base of the canvas, nearly illegible, in the artist’s now half-century-old, trade mark Victorian lettering.

Other canvases give more leeway in terms of imagery and decoration. An untitled work from 1998, for instance, in encaustic on canvas and wood with objects, has engraved lines of animals and signs of a vaguely archetypal nature on one half. On the other is an approximated argyle pattern, a rare admission of albeit muted color. No one could claim, however, that the painting luxuriates in its ornament or iconography. Whether it is mark-making, decoration, or imagery, Mr. John’s motto seems to be the Kantian dictum, purposiveness without purpose.

Matthew Marks has assembled a large show for this grand old man of the American avant garde, with countless variations on his singular themes. The show includes lots of printmaking. Mr. Johns lives up to a caricature of the reproductive media: his turgid, pretentious work in all mediums is about remoteness, repetition, technical fuss, and business for business’s sake. Coupled with his penchant for grayness and faux painterliness, this makes for a cheerless experience. With its endless loop of false leads and phony expressiveness, looking at a big show of Jasper Johns is like watching a beginner driver trying to park a car.

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Chuck Close might at first seem like a chip off the Jasper Johns block: He is the epitome of a worker bee, after all, moving with unvarying emphasis across his big canvases, patiently, laboriously filling in cube upon cube to build his ingeniously pixilated, gargantuan, photorealist portraits. But he is different in many ways.

Mr. Close is the opposite of a noodler. Each tessara is made up of organic, spontaneous-seeming, ornamental shapes, a funky array of naughts and crosses, not to mention sausages, boomerangs, and bagels. Iconic, and genuinely monumental, a Close shows itself to be composed of a bewildering matrix of seemingly unrelated marks. The resulting images are arrestingly enigmatic, like Byzantine mosaics. Portraiture a genre we take for granted more than any other; it’s so transparent and immediate that it takes particular courage, if not bloody-mindedness, to insist as Mr. Close does that like all imagemaking it is a peculiar exercise in craft.

Mr. Close was initially a meticulously austere, frankly, rather boring photorealist in his execution. His mark-making jollied up mid-career as the result of the savage neural disease that left him wheelchair-bound and severely restricted in his control of the brush. This forced him to adopt new, more painterly strategies. It sounds awful to say it, but his handicap made his art: The weird, wobbly vocabulary he has developed since his rehabilitation, allied to the pixilation that was already at the heart of his aesthetic, has generated rich layers of meaning and beauty remote from his art in healthier days.

The latest group of portraits include a couple of new sitters: Inka, the hot button artist Inka Essenhigh, and Herb, a family friend variously described as their lawyer and accountant. They also show some striking formal departures. Particularly intriguing is the treatment of eyes. Pupils and iris are readymade digits within the constellation of a face – small, perfect shapes not much bigger than Mr. Close’s pixels. Consequently around the eyes the arbitrariness, not to mention the anonymity, of his oddball shapes are in a kind of meltdown. The eyes duplicate, sorcerer’s apprentice-style to follow each other around the room.

Johns until June 25 (523 W. 24th Street, between Tenth Avenue and West Street, 212-243-0200).

Close until June 18 (534 W. 25th Street, between Tenth and Eleventh Avenues, 212 929-7000).