(Pocket-lint) - Brilliant though the TV world's new high dynamic range (HDR) technology is, it's also proving monumentally hard for current TV technologies to handle. Which is precisely why Sony has moved past "current TV technologies" and come up with something new for its XD9305 series: the Slim Backlight Drive.
The main trick of this new Drive is that it introduces unprecedented levels of local light control to the edge LED lighting systems favourited - for affordability reasons - by the majority of LCD TVs. Its trick is that it places two of the light guide plates required by edge LED TVs in sequence, rather than just sticking with the usual single plate.
This gives the XD93 twice as much potential for controlling the amount of light appearing in different parts of the picture. That's a big deal at any time, but a potential deal-maker in these days of HDR, where the need for more localised light controls has shifted to a whole new level.
So how does it fare and is the XD93 (not to be confused with the full backlight array of its bigger brother, the XD94) the 4K TV to plump for?
Sony KD-65XD9305 review: Design
Despite using two light plates instead of one, the slim backlight drive has also been created to deliver one of those ultra-skinny designs everyone seems to want these days. The 65-inch XD9305, reviewed here, is just 36mm deep at its thickest point, and for at least half of its rear it's actually far slimmer than that; not much deeper than your average 2016 mobile phone, in fact.
The build quality of what little there is of the TV frame is exceptional. Sony has even managed to find the space for a bit of showboating in the form of an injection of gold that runs through the centre of the XD9305's outer edges.
Even the desktop stand is classier than most with its tasteful aluminium sheet finish and graceful angles, while the new wall-mount option (included in the box) cunningly adds almost no depth at all to the TV.
Connections on the XD9305 are as you'd expect of a high-end TV in 2016: four HDMIs, for instance, can handle both 4K up to 60 frames a second and HDR content, while multimedia support comes via a trio of USB ports and both wired and wireless network connections.
Sony XD9305 TV review: Android and YouView
These network connections can stream multimedia from your DLNA-enabled devices, or bring you into contact with the huge world of apps Sony TVs now provide courtesy of their implementation of the Android TV smart platform.
It must be said, however, that Android TV is hardly the perfect smart TV system. Its full-screen interface feels clunky, and it doesn't provide as many customisation options as the best rivals. It also doesn't feel very focused compared with the finest smart interfaces, seeming to mistakenly believe that quantity usurps quality where smart TV interfaces are concerned.
Android TV also boasts one significant content weakness for all its hundreds of (largely pointless) game, video and information apps: its lack of UK catch-up TV services. Fortunately, Sony has got round this by also fitting the 65XD9305 with the YouView platform, which not only brings to the table all of the big four UK catch-up TV platforms, but also lets you access their on-demand content via a brilliantly simple electronic programme guide (EPG).
Sony KD-65XD9305 4K TV review: Picture quality
Turning to the 65XD9305's picture technology, the Slim Backlight Drive is not the only trick the XD9305 has up its sleeve. Also likely key to its success - especially in the HDR era - is its combination of a wide colour spectrum panel and proprietary Triluminos colour processing.
Plus there's Sony's previously impressive X1 processing chipset, which combines powerful control of all the key elements of picture quality with a vast database of picture source scenarios to help the TV first identify and then apply appropriate rules to whatever source type it happens to be receiving. This database covers and optimises the appearance of everything from the ropiest of YouTube feeds to the most pristine of Ultra HD Blu-rays.
To say the 65XD9305's pictures make a strong first impression would be an epic understatement. Pushing the TV to its maximum capabilities with a selection of 4K, HDR, wide colour gamut Ultra HD Blu-rays, there are times where the 65XD9305 delivers the best pictures yet seen on an edge-lit LCD TV, and arguably the best pictures yet seen on any LCD TV.
Colours look ravishing for starters, as Sony's Triluminos technology helps the screen serve up a truly dazzling combination of wide colour gamut vibrancy/saturations and mesmerising tonal subtleties that leave you in no doubt whatsoever that you're watching the next generation of picture quality unfolding before your eyes.
Sony XD9305 review: High Dynamic Range
The irresistible dynamism of the screen's colours also owes a big debt of gratitude to the impressive brightness Sony has managed to get from the 65XD9305. Its peak brightness just sneaks past the 1000-nit level recommended by the AV industry's Ultra HD Premium specification, and this brightness adds volume and punch as well as subtlety to the colours on show.
The 65XD9305's brightness in conjunction with the Slim Backlight Drive also creates a startlingly expansive dynamic range. This is particularly obvious at the brightest end of the HDR spectrum as Sony's TV throws up peak whites and colours that glimmer and shine with an intensity old standard dynamic range video can't even get close to.
The 65XD9305 is less emphatic in its handling of HDR's extremes at the darkest end of the light spectrum, as you might expect of an LCD TV. But there's certainly a big increase in the overall light range available to the TV for delivering enhanced shadow detailing in dark scenes, as well as that much more lifelike general look to images that is really HDR's main raison d'etre.
While the 65XD9305 looks at its most spectacular with the HDR/wide colour content it's pretty much being designed to deliver, though, it's also mesmerisingly good with the "old" standard dynamic range content we've been living with for so many decades. It's able to rein in its colours to match those of SDR pretty much perfectly, while the subtlety of its tones reminds you that while HDR represents the irresistible future of TV, SDR really has always been capable of looking pretty darned beautiful when it's done right.
Another great strength of the 65XD9305 is its handling of detail. With native 4K content its superb colour and - for the most part - light handling helps it deliver one of the most convincing and extreme displays of 4K's superiority over Full HD we've seen to date, unlocking the full potential of all those pixels the screen has at its disposal.
Sony XD9305 4K TV review: Its one picture weakness
While the 65XD9305's pictures look good enough to make a grown AV fan weep for much of the time, though, they also, sadly, have an Achilles Heel: the Slim Backlight Drive can't completely solve the seemingly inherent problems edge LED TVs have with delivering light on a sufficiently localised level to handle HDR's light extremes with absolute conviction.
The issue is this: while it's beyond dispute that the Slim Backlight Drive can deliver deeper blacks in the darkest picture areas - even in localised areas in the image's centre - than arguably any other edge-lit LCD TV to date, the way the Drive essentially separates the backlight into a series of individually controllable but large boxes can lead to some really quite abrupt and thus more distracting backlight divisions.
In other words, where very bright HDR objects sit against a very dark background you sometimes actually feel like you're watching a series of differently lit blocks rather than a single organic picture. At times you even feel that a less localised backlight approach would actually have delivered a more immersive experience - even though this more typical edge LED arrangement would not, almost certainly, be capable of reaching the same black level depths that the 65XD9305 can.
To put it another way, while the Slim Backlight Drive is certainly a promising and well-intentioned innovation by Sony, right now there's work to be done to make it a really effective HDR solution to LCD's ongoing light control issues.
Sony XD9305 4K TV review: Sound is slim too
Sony's new obsession with slimness has led to it ditching the huge magnetic fluid speakers that used to adorn the left and right sides of previous high-end Sony TVs.
This is a logical decision from an aesthetic and practical point of view - but unsurprisingly it's not a positive move where sound quality is concerned. Unless, of course, you fork out some extra cash and buy a separate soundbar or speaker system.
These predecessor TVs were arguably the finest sounding mainstream TVs ever... and arguably the least attractive too. The 65XD9305, by comparison, sounds sadly pretty average.
Bass levels are fairly limited and slightly cramped, the mid-range is clean but pretty narrow, and while there's a strong amount of treble detailing, this treble information can tip over into harshness when the going gets tough. Certainly consider that additional sound system, then.
There are times when the 65XD9305 looks like the best TV ever made - both in design and picture quality terms. Its handling of bright HDR/wide colour 4K content is really that good.
However, high-contrast HDR content reveals that Sony's well-intentioned bid to introduce a new level of edge-LED backlight control ultimately creates as many issues as it solves, leaving us with the feeling that this new Slim Backlight Drive technology is perhaps a transitional work-in-progress rather than the finished article.
Also the 65XD9305's quest for slimness leaves its sound compromised not just against the efforts of Sony's own previous equivalent models but also against the best audio efforts of its current rivals.
Put all this together and the 65XD9305 often looks nothing short of incredible, but isn't always the image of perfection.