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Edge LED backlighting isn't exactly the latest tech, but with eight million pixels to its Full HD's paltry two million, the UE55JU6400 has a leg-up on its rivals.
Detail and colour
Native 4k footage is hard to come by, but there are plenty of downloadable 4k-quality MP4 movie trailers online. Compressed they may be, but a 4k trailer of Interstellar shows off the UE55JU6400 at its best. A shot of deep space shows a backdrop of stars that's almost unfathomable; tiny pin-pricks of light that are bright white, while the background remains black.
Next comes Solar Rain of Fire, a close-up test sequence of the sun's surface. The pulsing surface is shown in incredible detail and vibrant colour by the UE55JU6400, while the contrast of bright orange prominences against the black of space, and the textured chromosphere, is simply stunning.
Turn to regular TV and the good work continues. There are four preset colour modes – Dynamic, Standard, Natural and Movie. The latter was our favourite. There's little to differentiate the Standard and Natural settings, though.
One rather strange additional feature here is Sports mode, which gets its own shortcut on the remote control, no less. When activated, it introduces a quite disgusting, over-exposed, over-saturated look that destroys detail, and gives green a weird kind of glow. It also increases the volume. It feels like going to an ad break while watching ITV.
Black levels and noise
The black levels on the UE55JU6400 aren't perfect – there's a definite touch of blue during some of the scenes in our test disc, The Earth – An HD Odyssey, on Blu-ray, though it rarely interrupts an otherwise sparkling colour palette.
It's clean, too, with HD material upscaled well. The only drawback is that anything shot with a standard-definition camera becomes immediately obvious; random panning shots and incidental footage during TV programmes do look soft and noisy.
Motion blur and viewing angles
The viewing angle of the UE55JU6400 is one of its major drawbacks; watch from the wings and there's a definite loss of contrast, with 4k footage taking on a slightly noisier look, too.
Blurring during panning shots isn't much of an issue, though it is occasionally detectable if you deactivate Auto Motion Plus. It's therefore best left in the standard strength.
Though the UE55JU6400's main menus lack the processing power required to make them tolerable, the Smart Hub is a breeze to navigate.
Since the new Smart Hub is all about easy access, it relies on a pop-up menu on the bottom screen rather than the full-page of previous incarnations. It's divided into two areas, labelled Featured and Recent.
The Featured square on the extreme left gives you one-touch access to launch Smart Hub as a whole, which is where you'll find apps, games, a web browser and everything else.
By default, Featured contains a link to apps and games, plus hot links to Netflix, YouTube, Amazon, Twitter and Web Browser, Smart TV, My Content (USB sticks and connected computers, etc) and Search.
In Recent, you'll find – yes, you guessed it – apps you've been using in the last few days and weeks, which also include inputs (such as the Blu-ray player), TV channels and a shortcut to an attached USB stick, as well as the likes of Netflix, Vimeo or Amazon Instant.
This works well in theory, though if you share a household expect the seven slots to quickly become filled with TV channels and apps you don't particularly want littering your shortcut spaces. A 'clear recent' option is a handy, though nuclear selection; happily, anything you purposely pin to the shortcuts is protected from being cleared by others.
However, actually setting up the apps is long-winded. Though the Apps pages are clear, concise and well laid out, only 10 icons are visible on the screen at once, which means constant remote-fingering. It also doesn't hide details for apps you've already downloaded; you can easily find yourself scrolling through pages of apps you already have while searching for a new one.
My Content takes you to a screen that can show what's on a connected USB stick, though it treats up to three sources separately. I prefer LG's source-neutral approach to digital content, though the UE55JU6400's is simple enough; choose the tab relating to the USB stick you want, and the software shows icons for folders on one side of the screen, with any space left filled by thumbnails of grabs from the video or photo files themselves.
However, those grabs are rather random; the backs of people's heads, shots of backgrounds and other meaningless images. They're also all arranged from top to bottom in columns, rather than from left to right, which would give it some at-a-glance glory.
It displays photos within a second or two, which is impressive, and though music means an unexplained trip back to live TV for a few seconds while the music software is opening, the song plays within a few seconds. There's a great jukebox mode, too, which allows you to cue up songs ahead of time.
There's nothing special about the the sound emanating from the UE55JU6400's speakers, but the sheer width of the TV does help lend some sense of stereo. That's probably doing it a disservice; gone are the tinny, harsh sonics from the flat TVs of yesteryear, replaced with some semblance of bass (though it can sound a bit false).
The UE55JU6400 has Samsung's usual presets of Movie (boosted low frequency for vocals), Amplify (boosted all-round, but slightly harsh vocals) and Clear Voice (kills background sound), though the Standard setting is the most balanced.
At its initial list price, the UE55JU6400 is too expensive, especially in the UK. It's all down to that under-powering of its core menus system, which just seems a crazy oversight on an otherwise smart, advanced TV. However, if you can find the UE55JU6400 – a 55-inch 4k TV, remember – for closer to £1,000/US$1,500, it would be hard to ignore.
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Jamie is a freelance tech, travel and space journalist based in the UK. He’s been writing regularly for Techradar since it was launched in 2008 and also writes regularly for Forbes, The Telegraph, the South China Morning Post, Sky & Telescope and the Sky At Night magazine as well as other Future titles T3, Digital Camera World, All About Space and Space.com. He also edits two of his own websites, TravGear.com and WhenIsTheNextEclipse.com that reflect his obsession with travel gear and solar eclipse travel. He is the author of A Stargazing Program For Beginners (Springer, 2015),