Eastman Kodak Co. created a new way to play the stock market yesterday when some resourceful speculators discovered they could buy the company's soon-to-be-worthless instant cameras to take advantage of Kodak's offer to exchange them for shares of its stock.

Until Kodak told stores to stop selling the Trimprint cameras, it was possible to buy one for as little $19.95 with the promise of trading it for a share of Kodak stock worth close to $50.

Kodak, forced out of the instant photography business by a court order, was flooded by more than 12,000 calls from owners of instant cameras who soon will be unable to buy film for them. At the same time, arch-rival Polaroid Corp. moved to capture some of the Kodak customers by announcing a special $10 discount for anybody trading in a Kodak instant camera to Polaroid rather than Kodak.

Those were the developments yesterday in the wake of a federal court injunction that overnight transformed 16.5 million Kodak instant cameras into what one investment analyst called "worthless items of trash." The order -- barring Kodak from making or selling instant cameras or film -- resulted from a 9-year-old court case in which Kodak was found guilty of infringing on Polaroid patents when it brought out its current generation of instant cameras in 1976.

Because only Kodak instant film can be used in Kodak cameras, the court order will render the company's instant cameras useless once current film supplies run out within the next few months.

"Those cameras are worth nothing right now," said Brian Fernandez, a photography industry analyst with Nomura Securities International Inc. "It was a camera yesterday; it's a paperweight today. Or maybe a museum piece."

But the speculators showed that, with a little imagination, even paperweights can be turned into tidy profits if you move when the price is right. Faced with the prospect of dealing with millions of irate consumers, Kodak late Wednesday announced a special rebate program in which customers could exchange their Kodak cameras, most of which were sold for between $20 and $30, for $50 worth of Kodak coupons or a telephoto disc camera worth $50.

A third option -- and the one that apparently excited the speculators -- was Kodak's offer to swap each Kodak camera for one share of its stock, which closed on the New York Stock Exchange yesterday at $47.50, down $1.37.

"It's amazing -- when opportunities like this come up, people really come out of the woodwork," said Fred Bell, senior vice president of W. Bell & Co., a Rockville-based chain of catalogue stores. "We've had speculators coming in trying to make a windfall. We even had some customers who were calling up and trying to reserve all of our inventories" of Kodak instant cameras, he said. The offers were swiftly rejected, but Bell said that, at some of his stores, customers were buying "five and 10 cameras at a time." Other local retailers reported similar evidence of unusual consumer interest.

"There was one guy -- he was waiting for me to open up this morning because he wanted to buy all the Kodak instant cameras I had," said Fidel Cuesta, manager of the Ritz Camera Center on K Street NW in downtown Washington. "He told me he wanted to exchange them." Cuesta sold him the two he had left.

Meanwhile, Kodak, whose toll-free hotline (1-800-792-3000) was swamped by more than 12,000 calls, also was receiving reports "of people who were trying to buy a dozen or two dozen," spokesman Charles Smith said. But the company acted swiftly to halt the profiteering. By mid-morning, it had contacted its distributors around the country and asked them to remove the hot-selling cameras from the shelves.

Smith said the company also has decided there would be a limit on trade-ins of three per household, thereby blocking the speculators from reaping huge windfalls.