Three crowd scenes hang side by side as photographic "Counterparts": a fleshy, waving, squinting mob snapped by Weegee (Arthur Fellig) at "Coney Island"; the business- suited throng that looks like dots of black and white in Arthur Siegel's "Right of Assembly"; and Margaret Bourke-White's wartime shot of a Nazi rally in Czechoslovakia.

They're visually similar while emotionally at odds, and that's the point in "Counterparts: Form and Emotion in Photographs," 100 photographs from the collection of New York's Metropolitan Museum of Art, at the Corcoran through May 8.

More than a third of the prints have never before been on public view. Included are works by Alfred Stieglitz (whose habit of comparing his friends' works inspired the format of the exhibit), Henri Cartier- Bresson, Brassai, August Sander and Andr,e Kert,esz.

Several of the groupings have patterns in common. All manner of water towers are chronicled in "one work in 16 photographs," while a serial portrait of an artist's face captures six moods. The distinction between emotion and sentimentality marks two photographs of couples; one showing husband and wife; the other, lovers but not love.

The body is the subject of a group of three photos: a masked woman naked except for a black fishnet stocking, black gloves, top hat and bathing cap; a naked man posing in a feminine attitude, a stomach-to-knees close- up of a very pregnant woman.

The show's accompanying text raises some heavy unanswerables: What is the purpose of photography? When is a photograph art? "Is the purest form of photography one in which the photographer collaborates with contemporary actuality?" And, say, what is "contemporary actuality" anyway? COUNTERPARTS: FORM AND EMOTION IN PHOTOGRAPHS -- At the Corcoran, through May 8.