Robert Rauschenberg sat there on the video screen, in full color, looking at the camera a bit tensely and blinking every few seconds. Around the darkened room in the Corcoran Gallery, similarly displayed on video screens, were the fellow artists who share with him the 36th Corcoran Biennial exhibition: Jasper Johns, Ellsworth Kelly, Willem de Kooning and Roy Lichtenstein. "Living portraits," the soundless videotape pictures were called by one of the Friends of the Corcoran Gallery who filed respectfully through the room at last night's private preview of the exhibit.

The three-dimensional Rauschenberg was less respectful. Confronting the videotaped portrait for which he had posed an agonizing 35 minutes, he gestured wildly: "Look! It's alive! It moves!" Who is the prettiest artist in the room, someone asked him, and he gestured toward the gaunt, whitehaired De Kooning on a nearby screen: "Old Willie over there," he said.

De Kooning was the only one of the five artists unable to attend the opening, but his presence was vividly felt, not only in his videotaped image but in the large, brightly colored canvases whose folwing forms dominated one of the rooms.

The other four artists moved easily through the cocktail reception which preceded the buffet dinner, chatting with people and enjoying themselves.

"I like the exhibit a lot," chuckled Roy Lichtenstein, whose massive paintings in eclectic comic-strip style brightened the walls of a corner room. "Obviously -- I'm part of it, but I really do like it. I like the way it's hung. I like the other people in it."

"Well, what do you think of it?" Ellsworth Kelly asked a partygoer, standing only a few feet away from Lichtenstein. "We do it for you ," he said.

Kelly expressed discomfort about the video portrait. "I resisted it at first," he said, but then he began to talk as an artist about the idea of such a portrait: "It's an interesting idea, like the early photographer Mathew Brady, who did so much work in the Civil War. You had to sit for 25 minutes for one of his photos, and looking at them you have a sense of time passing in them."

Then, looking down into the depths of his cocktail, "But I don't think I'll like mine. I don't like photos of myself."

Jasper Johns peered into the room that was wildly alive with the big, busy Lichtenstein paintings and shook his head thoughtfully. "Mine look a little dinky," he said. "I wish they'd hung a few more. These rooms are so glamorous; I wish my pictures were bigger." He burst out laughing, then continued in this self-deprecating vein:

"I'm a slow painter... I think I worry about productivity. Wouldn't you say six paintings a year is slow?"

He was asked what he thought about the video portraits. "I had to do that twice," he exclaimed. "See, I took twice as long as everyone else for that, too. There was a tree in the background the first time, and it would keep moving, and it looked very ominous -- like the end of the world or something -- so I had to do it over."

Recalling his videotape session, Rauschenberg said, "I hated it when it was being taped. Before, I would go and practice in the bathroom.... I'd look in the mirror and practice making a face." He demonstrated a solemn, wide-eyed stare. "It didn't work! After 15 seconds, I'd break up!"

Among the art-dealers present, Leo Castelli was understandably pleased ("I'm very proud of them and of myself, too"), since four of the five artists were his proteges. Franz Bader's reaction was less predictable. "There are some very exciting paintings here," he said, "but please don't quote me. I have a reputation as a reactionary, and I don't want to disappoint people."