LAS VEGAS — The race to make TVs larger and larger has created a colossal problem for manufacturers: As screens grow, picture quality worsens — unless the viewer moves further away from the screen.

The issue is playing out in cozy dens and family rooms around the world. To get the full benefit of a large high definition screen, viewers must move back from their sets. Since the ideal viewing distance is no closer than three times the height of your screen, or about one and a half times the diagonal length, big TVs have literally forced many families’ backs against the wall.

This year, TV makers are doing their best to give huge-screen fanatics more breathing room. New “ultrahigh-definition” sets were shown off Monday by companies such as LG and Sharp at the International CES gadget show in Las Vegas, with other makers set to follow suit. Consumers tend to buy a new set every seven years or so, and television manufacturers are hoping the technology will give consumers a reason to upgrade.

With nearly 8.3 million pixels, an ultrahigh-definition screen contains four times more pixels than an HD TV. Because of the higher resolution, viewers can sit close — according to some estimates, as close as the diagonal length of the screen, which is about a third closer than before — without losing clarity. That could appeal to big-screen fans who live in small spaces.

Ultra-HD sets come as small as LG Electronics Inc.’s latest model, which stretches 55 inches diagonally. And estimated prices are dropping from the tens of thousands to below $10,000, bringing these multi-megapixel TVs well within the spending range of early adopters.

It could be a few years before prices come down enough for the masses to justify buying ultra-HD TVs, especially considering that the U.S. TV buyers spent a record-low average of $364 on flat-screen TVs during the recent holiday shopping season, according to research firm NPD Group.

Hampering sales even further, ultra-HD faces another problem: There’s very little content. Since 2004, only about 50 movies have been shot with an ultra-HD camera. They include the James Bond hit “Skyfall” and the Batman sequel, “The Dark Knight Rises.” Only a handful of movies shot on film, including “Taxi Driver,” have been converted to ultra-HD.

Sony Corp.’s 84-inch ultra-HD model, which it unveiled in November, comes with a computer server capable of storing and playing back giant movie files. It’s definitely not affordable for most people, however, and the TV unit with the server thrown in has a price tag of $25,000.

There’s also currently no standard way for upgrading Blu-ray players and discs to handle the ultra-HD format, although plans are in the works. Broadcasters are also a few years away from an upgrade. LG said its ultra-HD set will have upscaling technology to make regular HD images look better but a demo wasn’t immediately available.

The file sizes of ultra-HD movies will only be about 25 percent or 30 percent larger than similar HD files, according to Pete Lude, the president of the standards-setting body, the Society of Motion Picture and Television Engineers.