LG and Sony have both introduced Ultra High Definition (UHD) TVs with 84-inch screens within the past three months and both are priced at US$20K or more. These monster televisions have 16:9 aspect ratio UHD screens (3840 x 2160 pixels). There are no more than a few hundred UHDTV sets available worldwide, but given the price, that should be sufficient to satisfy the Christmas demand.

Imagine that a Christmas miracle happens, and an 84 inch UHDTV finds its way under your tree. The very next thing on your to-do list is amazing your friends and neighbors with the unimaginable clarity of a UHDTV screen. If it looks like the blank screen Sony pictured above, no one will be very impressed. To show off a television, you need a video source matching the screen resolution, so, brimming with pride in your new UHDTV, you reach for ... what?

The world of home video entertainment is dominated by 1080p format HDTV. Satellite dish? 1080p programming at best. Cable? 1080p. Your 50 GB Blu-ray discs are chock-a-block full of wonderful 1080p video data, but such will not properly show off your UHDTV.

Hold on – these UHDTVs can upconvert HDTV video into 4K UHDTV video. Doesn't that cover the amazement requirement? Sorry, but as much as the salespeople would like to convince you otherwise, when you upconvert an image you lose resolution and contrast – all you gain is an assortment of video artifacts. Nice as a novelty, but ... lacking ... in amazement.

Uber gaming screen? Well ... no. Even though Sony's upcoming PlayStation 4 is rumored to have a 4K output mode, the highest definition art in current video games is stored at HDTV resolution. The actual resolution of games will be HDTV until some true (and likely truly expensive) 4K games are developed from the bottom up.

The one place that 4K content can be easily found is your local theater. Nearly three-quarters of the 100,000-plus worldwide movie theater screens have 4K digital projectors – a nod to James Cameron's 2009 film Avatar. Since then a number of truly 4K films have been screened. The Hobbit will be the first digital 4K movie to be shown at 48 frames per second, and Sony is currently in talks with Blu-ray about making 4K Blu-ray-based versions of their upcoming reboot of Spider-Man available for home use.

"Blazing Bristlecone", a single frame from "Timescapes", won Tom Lowe the Royal Observatory Greenwich Astronomy Photographer of the Year award in 2011 (Photo: Timescapes)

There is even a 4K movie called Timescapes, a lushly visualized 50 minute memento of the American Southwest available as a 330 GB video file on its own hard drive. It is in the Cineform codec, a nearly lossless format used in 4K theaters. That surely takes care of the amazement requirement? Yes – if you can play it.

Here's one of the dirty little UHDTV secrets – HDMI is currently not able to transfer native Ultra HD video. HDMI cables are able to carry an UHD bitstream, but there is no HDMI standard for coupling an UHD video signal into an HDMI cable. (DisplayPort works with UHD, but neither the Sony nor the LG Ultra HD TVs have DisplayPort connections.) Sony engineers are currently developing a converter box able to accept native Ultra HD via a bank of four HDMI inputs. This converter would then output the Ultra HD signal via a single HDMI to the projector. It is not known how LG is addressing this problem.

Sony is sensitive to the content problem, and has the resources to provide a solution that will indeed amaze your friends and neighbors. Everyone who buys a Sony UHD television will be "loaned" a US$25,000 Sony UHD video player, together with a set of ten UHDTV movies newly mastered from theater releases or original filmed versions. The loan is open-ended, with Sony noting that it will not be going into customer's houses to repossess the video players.

The movies include The Amazing Spiderman, Taxi Driver, and The Bridge on the River Kwai. In the end, it would appear that Sony will quench the need for amazing Christmas demonstrations of new technology, as long as that video player is available and delivered before Christmas. After all, what would Christmas morning be without a little suspense?

Product pages: LG, Sony