Eastman Kodak shares plunged 15 percent on Thursday after a U.S. trade panel upheld portions of a ruling unfavorable to the company in a patent fight over digital camera technology in cellphones.

The U.S. International Trade Commission sent portions of the case back to its internal judge for further review.

In January, the judge had found that Apple and Research in Motion did not infringe Kodak's patented technology because it was invalid.

The commission said it was affirming in part, reversing in part, and remanding in part the prior decision.

Kodak's Chief Executive Antonio Perez had previously suggested the company could reap $1 billion from a favorable ruling.

Kodak filed its ITC complaint against Apple and RIM in January 2010, arguing Apple's iPhone and RIM's camera-enabled Blackberry infringe on a Kodak patent related to a method for previewing images.

It asked the ITC to bar the importation of Apple and RIM mobile phones and other wireless devices with digital cameras.

Apple filed a countersuit at the ITC, accusing Kodak of infringing its patented technology. In an initial ruling, Kodak was found not to have infringed.

The ITC's notice on Thursday gave a brief summary of an opinion to be issued later.

The internal judge had found in January that Kodak's patent was invalid, which means it could not be infringed. The full commission, in its statement, asked the internal judge to reconsider the invalidity decision but said it took no position on the question.

On the issue of capturing a still image while previewing a moving image the ITC said: We find that the Apple iPhone 3GS and iPhone 4 do not literally infringe the asserted claim in their non-flash-photography modes of operation.

But it said the accused products from Apple and RIM did infringe a portion of the technology involving color patterns.

We are gratified that the commission has decided to modify in our favor the judge's initial recommendation, said Laura Quatela, Kodak's general counsel, in an emailed statement. As we have said from the start, we remain extremely confident this case will ultimately conclude in Kodak's favor.

Kodak also has related lawsuits pending against RIM and Apple in federal courts in Texas and New York.

The ITC set a target date of August 30, 2011, but said the administrative law judge could himself extend the date based on the need for further proceedings.

Shares of Kodak have moved sharply on developments in the case. They rose in March on word the ITC would review the judge's decision.

(Reporting by Diane Bartz; Editing by Tim Dobbyn)

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