A brand usually found in the lower echelons of the flatscreen TV market, Toshiba is making a bid for the big time with this huge LED screen. The trouble is, the 55SV685DB's very large price heaps on the pressure; is it much better than a 50-inch plasma, which now go for under £1,000?

However unlikely that might seem, Toshiba has strived to make the 55SV685DB seem good value by packing in some new features. The first, and most important by far, is LED backlighting. The 55SV685DB uses perhaps the most comprehensive form of the new tech, called "local dimming" or "full LED" by some brands. Instead of a backlight that's always switched on, rows of tiny LED lights line up behind the LCD panel. Capable of switching on and off individually, it's possible for the screen to show total darkness in one area of an image, and bright white in another.

The second crucial feature is Active Vision M200, a 200Hz anti-blur system, though a film stability mode (aimed at removing that annoying judder in all Blu-ray discs) Toshiba's much-hyped Resolution+ upscaling tech for digital TV and DVD is just as important on a screen of this sheer size.

The 55SV685DB's other features seem frivolous in comparison. Take its SD card slot, an unusual find away from Panasonic's Viera TVs. It's there to provide JPEG photographs for the Picture Frame mode, though the TV itself has so little onboard memory that instead of a slideshow, just a single picture can be transferred – and it's slow to load, too.

Just as distracting is the 55SV685DB's stilted stab at DLNA networking. Fetching digital media from a PC or Mac on the same home broadband network is a fantastic idea, but, like a lot of brands, Toshiba hasn't got anywhere near perfecting it. After quickly finding a networked computer, a slow and rather brutal process begins; a file type must be selected, then a specific file, before finding out whether it's compatible (only AVI and MPEG videos seem to be). The system gets ahead of itself by trying to display thumbnails photos/videos, but they never load and just slowdown the process further (Toshiba may have solved this issue on its Japanese-only Cell Regza 55X1, which offers 143 times more processing power).

The remote control doesn't help; it's unable to cancel commands and return to the previous menu, extending the agony. It's a similar story with the Media Player feature that reads files from a USB stick. 

Resolution+ also fails. The 55-inches of LCD screen just cannot display DVD or digital pictures coherently – digital artefacts and fuzzy edges are everywhere – which leaves the 55SV685DB looking rather forlorn and in need of a phenomenal performance with Blu-ray.

And it makes a respectable stab at greatness. Its LED backlighting is endlessly tweakable, with dynamic bars showing ambient light (plotted on a graph, even!), alongside the light output of each pixel.

And a high-def picture is indeed worthy of such examination. Black areas of the picture are jet-black, with plenty of subtle detail within. And subtlety is everywhere; bright whites, incredible colours and entrancing detail make for a picture that's lusciously cinematic. It's helped by an effective film mode that helps create a smooth image with sharp, well-defined edges even when objects are moving rapidly across the screen.