The exhibition “Retratos,” which opens tomorrow, contains nearly 115 works by artists from 15 countries. A monumental undertaking, it is the first comprehensive show of its kind. And although there are some familiar names – Frida Kahlo, Diego Rivera, and Rufino Tamayo, Fernando Botero, and Jose Campeche – most of the artists (nearly 40 of which are “unknown”) were new to me.

The show’s cultural point of view varies considerably from place to place and period to period. Pre-Columbian ceramic portrait vessels certainly served clearly different functions than paintings in oil on canvas produced after the Viceregal Era. There is something distinctly Latin American about the best works in the show. At its best the show is not really about portraiture in Latin America but about a Latin American point of view – a stance that holds despite the numerous and violent influences of other cultures.

A vein that runs all the way from the Peruvian earthenware vessels of the Moche culture (c. A.D. 100-600) to the Buddhaesque, Mayan earthenware masterpiece “Seated Dignitary With Cape and Headdress” (c.A.D. 600-900) to the haunting, handheld 18th-century death portraits on ivory and bone to Frida Kahlo’s “Self-Portrait With Thorn Necklace and Hummingbird” (1940). These works are boldly frontal, dignified, sober, and somber; this lends the show a freshness and a sense of “other” usually available only through a visit to a national museum in another country. This experience is enhanced by spectacular and unusual frames, some of which are more interesting than the portraits themselves.

The problem is that the all-inclusive exhibition – which includes genealogical manuscripts – is too large. “Retratos,” whose works are mainly from the 18th through the 20th centuries, throws too wide a net and still has considerable holes. There is little Aztec or Mayan work, nothing in the show from 900 to 1492, and shockingly absent is anything by the Uruguayan Constructivist master Torres Garcia. The catchall theme of the portrait is really too thin to carry the show, which could have been divided into two or three large, separate shows that focused on particular regions, portrait genres, or periods.

Walking through the exhibition, I often felt a tug of war between influences, a struggle for artistic independence, going on within the works. The majority of the portraits are mediocre or are so dependent on European or Northern American influences, traditions, and artists that they become pastiches and lose the very Latin American qualities that give them their unique cultural feel. This is especially true of the portraits from the late 19th century onward.

These portraits, whether realist, Cubist, synchromistic, or conceptual and theory-leaden (as in the show’s very weak Modern and contemporary sections) are derivative, illustrative, and academic. The one exception is Kahlo’s original and inventive “Self-Portrait” – a painting of the artist, wearing a necklace of thorns from which hangs a dead hummingbird (a love charm), and who is surrounded by foliage and insects and flanked by a spider monkey and a black cat (the two traditional symbols of lust and infidelity).

This is a shame, as the show is beautiful up until about 1860. “Retratos” begins forcefully in the first gallery, with Jose Campeche’s charming dual portrait, “The Daughters of Governor Don Ramon de Castro” (1797), then moves immediately into some of the most striking and powerful works in the show, a handful of Pre-Columbian earthenware and stucco portraits.

These sturdy portrait vessels, each of which uniquely portrays the sitter’s character, age, and temperament, are broad and taut and stare forward with wide, almond-shaped eyes. Short and stout, they sit on their truncated necks and look like severed heads striving to keep their pursed mouths above water. Upside-down, Y-shaped handlespouts grow out of the tops of their heads and look like strange pincers that, through pain, give them strength. The heads are rubbery, serious, and heavy, weathered in a range of reddish browns and creams, and their demeanors and expressions convey suppressed growls that set the tone for the entire show.

Other great works include the portraits of nuns, children, gentry, and the deceased. “Madre Maria Encarnacion Regalado,” by an unknown artist (c. 1860), portrays the nun as both child, when she entered the convent, and abbess, which she later became. She is as muscular as architecture, yet the scale of her child-body and her delicate and inquisitive, mask-like face betray innocence, fear, and wonder. Her black habit is magically both volume and void and firmly frames her face, which feels ready to pop under the pressure.

There are also a number of wonderful, very small portraits on view. “A Gentleman of the Canals Family Wearing Spectacles” by an unidentified artist of the Puerto Rican school (1840-55), a watercolor on ivory just under 3 inches high, glows a ghostly pearl, black, and Prussian blue. And “Death Portrait of a Lady” by an unidentified artist of the Mexican school (1850), a 3-inch-high gouache on bone, curves, swells, and envelops the deceased in a red pillow and green drape that are both softly caressing and tensely constraining.

Other works are wild and strange; familiar yet unfamiliar; contemporary yet out of this world. Abundio Rincon’s “Fray Francisco Rodriquez, Padre de Concula,” Mexican (1853), of the priest wearing sunglasses, looks like a portrait of Paul Schaffer. Some of the paintings feel French, Flemish, North American, or English. There are hints of Poussin color and Watteau frivolity, naive folk art, and van Dyck stature. “Woman from Puebla With Small Bouquet of Roses” (Mexican school, mid-19th century) looks like a better early Botero. Emanuel Lopez’s “Dona Maria Sanvia y Aguilar” (Mexican, late 18th century), a portrait of an old woman wearing an ethereal white shawl, feels as if it were carved from stone. And though it resembles a self-portrait by Grandma Moses, this work blows everything she ever did out of the water.

Until March 20, 2005 (1230 Fifth Avenue, at 104th Street, 212-831-7272).