LOS ANGELES — Keith Kaplan loves his two Sony televisions, one of which has served him well for a dozen years and continues to chug away in his bedroom in Santa Monica.

But when the 47-year-old limousine service owner recently decided to treat himself with a high-definition flat-screen TV, he picked a Panasonic set.

"I couldn't find any Sony TVs I liked," said Kaplan, who plunked down $3,500 for the 42-inch plasma set. "This one just had the best picture, and it was a good price."

Kaplan isn't alone among customers who are turning away from Sony Corp. for their TV purchases.

In the shift from cathode-ray tube TVs to flat-panel displays, nimbler rivals have nibbled away at Sony's dominance, narrowing the gap in quality and aggressively undercutting the Tokyo-based electronics giant on price.

"Sony's products have always commanded a price premium because it was Sony," said analyst Michelle Abraham of In-Stat, a market research firm in Scottsdale, Ariz. "But consumers' willingness to pay that premium is eroding. ... You can no longer assume that the other brands aren't going to be as good. It's an ongoing issue that Sony will have to face."

That's a dramatic shift from the days when Sony's Trinitron sets garnered as much as 50 percent of the high-end television market and represented about 20 percent of all TV sets sold, according to market research firm Envisioneering Group in Seaford, N.Y.

Sony still commands considerable clout and market share in the $77 billion global TV business. The company sold $8.9 billion worth of TVs in the fiscal year ended March 31, up 3.4 percent from the year before; that represented 13 percent of total revenue.

But the company has struggled lately to keep up with a raft of low-cost competitors operating in China, Taiwan and South Korea, especially in the market for large flat-screen sets. Indeed, Sony last month blamed sour first-quarter financial results on its TV business, which suffered a 21 percent drop in revenue from a year earlier.

Company executives acknowledged that they were caught flat-footed when TV prices fell far more this year than they had projected. The price plunge has prompted Sony to lower its overall sales projection for its full fiscal year by 3 percent to $67.8 billion and its net income forecast to $93.5 million, down 88 percent from its April estimate.

Sony chief financial officer Nobuyuki Oneda, in announcing last quarter's results, said prices plunged across the world in all TV technologies. Prices for TVs with liquid crystal displays, or LCDs, are expected to drop 50 percent in Europe this year, he said. In the United States and Japan, the declines are projected to be 20 percent and 30 percent, respectively.

Although Sony has deeply discounted its prices, competitors have cut even more.

Some analysts say the Sony brand, though still strong, has less cachet than it used to.

That creates opportunities for companies such as Dell Inc., the No. 1 personal computer maker, to sell low-priced plasma and LCD TVs sight unseen through its online store. Because Dell sells directly to consumers and does not need to share profit with retailers, it can generally offer lower prices.

"In our research over the years, we've found that the number of people who make their technology buying decisions based on brand goes down every year, while the number who base it on price goes up every year," said Josh Bernoff, analyst with Forrester Research in Cambridge, Mass.

The emphasis on value presents a challenge for Sony, whose traditional approach has stressed high quality at a price premium. But with TV components increasingly coming from a handful of common suppliers, standing out from the crowd becomes more difficult.

"While Sony continues to have a good reputation for innovation, it's become harder to maintain differentiation in the big-screen TV segment because they're all starting to look alike," Bernoff said. "That's because many of the components for these sets are often manufactured in the same places."

That's the case with Sony's plasma TVs. Sony has had to buy its plasma screens from South Korean and Chinese suppliers and thus rely on what is essentially generic technology.

Until recently, Sony had to turn to outside manufacturers for its liquid crystal display screens as well.

But Sony executives say they are taking steps to regain their footing.