Panasonic TX-48AS640 (AS640) LED TV Review

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Does mid-range mean middle of the road performance?

by hodg100 Jun 20, 2014 at 12:52 PM

  • TV review


    Panasonic TX-48AS640 (AS640) LED TV Review
    SRP: £1,000.00

    What is the Panasonic TX-48AS640?

    So now it’s the turn of Panasonic’s AS640 to come under the AVForums microscope.

    We got a really good look at the current flagship 4K AX802 just a little while ago and it left us with confidence that Panasonic’s post-plasma era carries some hope. The AS640 is something of a curio in that it’s the company’s only active-shutter 3D Full HD TV for 2014 and, therefore, likely possessed of a panel that will outdo the others in terms of contrast performance. It’s also a retailer exclusive – it won’t take you long to find out which one.
    As far as we are aware, this is also Panasonic’s first-ever television with a 48-inch screen but there’s also the 40AS640B and TX-55AS640 in the series. The first two digits represent the screen size, by the way. Probably the most important digits as far as this review is concerned are ‘749’ as that’s the amount of pounds this TV is commanding at the time of publishing, although there is a £250 discount built-in, that we can’t guarantee will last. So whether it’s a £500 or £750, let’s see if the TX-48AS640B merits it.

    Panasonic TX-48AS640 Design & Connections

    Panasonic’s new found confidence in TV design manifests in quite a bold design for the AS640. The two-tone bezel – black at the sides, silver top and bottom – is unusual but probably looks better when the TV is off, rather than on, where it can be slightly distracting when viewing with the lights up. The chassis of the TV is quite thick, by recent standards, but that’s a reflection of the fact that, thankfully, manufacturers are eschewing edge-lit LED for backlit modules, so we welcome the added heft.

    Even with the slightly unusual cut-out base stand attached it’s still extremely light, however, especially coming from the incredibly heavy AX802. We were slightly miffed that the AS640 only has inputs for 3 HDMI sources but at least two are downward facing, and one of those is your ARC (Audio Return Channel) compliant port for your soundbar or AV Receiver. The third HDMI connections faces out sideways and is much too close to the edge to prevent wires poking out without use of some sort of adapter. Also on the side are 2 USB ports and a headphone jack, whilst a Scart socket and component terminals complete the rear facing connections. Naturally you also get a Freeview HD tuner and a digital audio out.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Design & Connections
    Panasonic TX-48AS640B Panasonic TX-48AS640 Design & Connections

    There’s nowt fancy about the standard remote control supplied in the box, in fact it’s a throwback to their 2008 collection. Still, it gets the job done with a sensible size and quite large and easy-to-find buttons. You do also get an altogether more smart controller, also in black, with a stripped back button set, voice control and a touch pad for easier scrolling. It works well in practise and we can imagine many will be happy to dispense with the boring old controller.

    Two-tone bezels - the jury is out

    Panasonic TX-48AS640 Menus

    The major change to Panasonic’s menu system this year, in terms of usability, is that they scroll down all the way from top to bottom and no longer wraparound within their individual categories. This is not so bad in most submenus but can be an annoyance in the Picture Menu where there are a lot of options including a choice of viewing modes. Your best bet for some out of box accuracy here is True Cinema which also has has an extremely comprehensive set of finer calibration controls to accompany the usual suspects. The AS640 does employ some form of dimming system, although it’s not clear from the naming of the options under ‘Adaptive Backlight Control’ whether it’s a global (probably useless) or local (hopefully decent) system.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Menus
    Panasonic TX-48AS640B Panasonic TX-48AS640 Menus

    Panasonic TX-48AS640 Features

    There are two new major elements to Panasonic’s 2014 Smart TV platform. The first thing is Freetime which means they can match Samsung in being able to claim possession of all the major UK catch up services, i.e. BBC iPlayer, ITV Player, 40D and Demand 5. There is also the new MyStream feature, which is a scrolling, personalised recommendation screen, dragging in content from the likes of YouTube. Other than that, things are very similar to last year which means we keep the excellent my homescreen interface and a range of excellent apps, all wrapped up in a shiny silver presentation. We’re still at work on a dedicated review of the whole platform so we’ll update here when we’re finished.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Features
    Panasonic TX-48AS640B Panasonic TX-48AS640 Features

    Freetime is a big win for the Smart TV Platform

    Panasonic TX-48AS640 Test Results

    Pre Calibration

    Even when setting the Contrast and Brightness controls, it was pretty obvious that the greyscale tracking was already in pretty good shape. Measurements revealed that green was a little dominant and red energy slightly lacking but there was still a good degree of neutrality. Given the capabilities of the panel and our dark room conditions, we targeted a gamma response of 2.3 and the 2.4 pre-set was actually very close to that. The pre-adjusted colour performance was even better with over-saturated green and blue primaries over-saturated and red being the opposite the only points of note.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results

    Post Calibration

    Panasonic provides all the tools for the job, with 10-point Gamma and White Balance controls and a full colour management system, and it proved fairly easy to get things how we want them. We hardly had to touch the 10-point gamma controls, as it happened, as the equivalent White Balance controls were extremely effective. With a highest delta Error measuring just 0.38, we really have no concerns whatsoever in this department.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results

    The CIE Chart, top-right, reveals that we weren’t able to fully saturate red – at least not without messing up the hue and luminance elements to an unacceptable degree. We were able to fix all the other small issues leaving us with an excellent set of results at full stimulation levels. We can see from the expanded CIE diagram below that colours also tracked extremely well at lesser saturation levels, which bodes well for very natural looking images.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results
    Contrast, Black Levels & Screen Uniformity

    A backlit panel brings with it the promise of all manner of advantages over the edge-lit equivalents. First and foremost, it should make the job of dispersing light more evenly across the screen an easier job and the AS640 was very admirable in that regard, indeed. In fact, it was better than the flagship 4K AX802 in this regard, which was particularly evident when showing full – or fullish- one coloured screens. The AS640 also has an effective dimming system, that seemed to act like the equivalent of the AX802’s ‘Standard’ setting, although ‘Adaptive Backlight Control’ is a simple On/Off deal on this TV. With it engaged, we got averaged black measurements of 0.055 cd/m2 from a chequerboard pattern, giving us an ANSI contrast of around 2,200:1 when set against averaged peak whites of about 120 cd/m2. That provides for very impressive black levels in almost all circumstances that are really helped by the fact the screen is a uniform black.
    Panasonic TX-48AS640B Panasonic TX-48AS640 Test Results
    Video Processing

    The first thing to deal with here is a very odd quirk. Without the Intelligent Frame Creation (IFC) setting engaged at all, content via a 50Hz signal is near unwatchable owing to a very distracting judder. We at first suspected it might have been that the Film Cadence mode was set to on and the AS640 was treating our TiVo’s 1080i50 signal as progressive, but it’s not that. We took our K-10 to the screen to measure the screen refresh but it was generally around 100Hz (as expected) so we’re left clutching at straws at to what is the cause. The effect looks like what you get when you see a shoddy 60Hz to 50Hz conversion so perhaps 60Hz is what the TV is ‘expecting’ by default. Whatever the cause, it needs to be addressed. That said, we commissioned a survey that concluded more than half of the UK public never change any settings, which will mean most folks will be watching the AS640 in the Normal Viewing Mode which has IFC at Max by default. That causes its own issues but it’s preferable to the jerk-fest with it off. In True Cinema it’s on ‘Min’, at stock settings, so it’s not likely to be something that is going to cause much consternation but it’s a strange one indeed. We have fed back the issue to Panasonic and we'll update the review if and when we hear back from them.

    What's with the 50Hz judder?

    With IFC set to ‘Min’ things were a lot better. In fact, for most of the time, the AS640 then behaves as you would expect with it set to ‘Off’. That setting introduces very few of the usual artefacts and produces motion handling that is generally clear and natural looking. Strictly speaking the AS640 didn’t pass the 2:2 PAL cadence test with IFC engaged but the smoothing was sufficiently good you’re unlikely to notice and video deinterlacing was also well implemented with a minimum of jaggies on the likes of halfway lines as the camera pans. The Football World Cup (ongoing at the time of publishing) is good news to a TV reviewer in more ways than one! The AS640 also treats Standard Definition signals with respect and scales very ably. This should be no great surprise as nearly all half decent TVs can handle this task competently nowadays, but merits mention nonetheless. The same could almost be said for coping with the demands of 1080p24 (most Blu-ray discs) and there were no issues here, either, with smooth handling of film based material showing no induced judder or artefacting.

    Gaming Performance

    By switching in to the Game Mode from the Options submenu in the Picture Menu, it is possible to reduce input lag down to 57 milliseconds, bar Dynamic, which is slightly lower at 52. Neuther figure is likely to thrill a really competitive gamer but it proved sufficient for our trivial single player pursuits. You can get Dynamic in to some sort of usable state with the picture controls but for 5 milliseconds, we’ll pass.

    Energy Consumption

    • Standby: 0W

    The following measurements were taken with a full screen 50% white pattern:

    • Out-of-the-Box – Normal Mode: 61W
    • Calibrated – Professional Mode: 58W
    • Calibrated - 3D Mode: 103W

    Panasonic TX-48AS640 Video Review

    Panasonic TX-48AS640 Picture Quality - 2D

    So this is the second consecutive Panasonic LED TV we’ve had in for review boasting great native contrast performance and what a difference it makes to the enjoyment. Everything just has more punch and dynamism with the highly accurate colours the icing on the cake. As we mentioned above, you can even improve the perceived dynamic range by utilising the dimming system, labelled ‘Adaptive Backlight Control’ without introducing any major flaws. We put the system through its paces using some scenes in The Tudors, that contain a lot of flickering flames in dark rooms, and the AS640 came through extremely well, with only momentary lapses where small areas of the screen were too bright but it’s a world away from Panasonic’s implementation last year – and that’s a good thing! The like of movie credits will show some haloing effects where the surroundings of the letters will be a bit over-Illuminated but for most ‘real world’ content it’s very effective and worth engaging.

    The compromise in Panasonic not going with their usual IPS type panels is in viewing angles. To be fair, in terms of blacks washing out, the AS640 actually fares very well at more acute watching positions but the colours fade quite noticeably from more than thirty degrees off-centre. This probably won’t be an issue if you put the TV in a corner of the room but if it’s in the middle of a wall, those not in the box seat may suffer a little.

    Great blacks, good dimming and near-perfect colours, what's not to like?

    We don’t want to make too big a deal of the viewing restrictions, as it’s fairly typical of the technology, and those sitting within the sweet spots will be treated to some very nice pictures indeed, whatever it is they are watching. There’s a World Cup on, in case you hadn’t noticed, so we’ve given the AS640 plenty of opportunity to show its sporting prowess. We’re happy to report that the excellent dark screen uniformity is almost matched when there is colour on screen. We did pick up on an extremely mild dirty screen effect, evident in some panning shots over the grass, but it was infrequent enough not to distract.

    As we’d expect from an LCD/LED TV, images – static ones, in particular - look extremely sharp and detailed and the capability of the panel to go very bright means you can expect some very vivid (in a good way) pictures which look a treat with the likes of a well shot nature documentary. The long and short of it is, we really enjoyed our time with the TX-48AS640 and we hope Panasonic sees fit to extend its range to include more panels like this going in to 2014, beyond a ‘special’ model of potentially limited availability. Oh, and if you skipped the ‘Test Results’ section of this review (how could you?), remember that you will need to put/leave IFC in its ‘Min’ setting when watching broadcast TV or your DVDs!

    Panasonic TX-48AS640 Picture Quality - 3D

    The AS640 is a largely excellent 3D television. The colour palette of the review sample looked very accurate in the True Cinema 3D mode and although black levels are very slightly elevated, when compared to the 2D modes, the dimming nature of the specs means you lose next to nothing in contrast performance. Motion handling for 1080p24 Blu-rays was pretty much flawless, without any assistance from the ‘24p Smooth Film’ setting and our test clips of broadcast 3D content at 50Hz, showed none of the judder issues seen with the 2D, without IFC engaged. The Wimbledon clips did reveal some ghosting with the tramlines of the court, but that happens with almost every 3DTV we test, and the general performance of the AS640 will no doubt thrill fans of the format, with loads of depth and pop-out when called upon.


    OUT OF


    • Great blacks
    • Good dimming system
    • Near perfect colours
    • Generally strong video processing
    • 3D has loads of pop
    • Solid Smart TV features


    • Judder issues with 50Hz content without IFC on
    • Very mild 'dirty screen effect'
    • Colours wash out off-axis
    You own this Total 0
    You want this Total 0
    You had this Total 0

    Panasonic TX-48AS640 (AS640) LED TV Review

    We’re not sure if we’re totally sold on the two-tone black and silver bezel of the AS640, although it only ever distracts in really bright conditions but it’s certainly a very contemporary design that many will like. It’s actually pleasing to see a TV that doesn’t feature a super-slim bezel, as it promises superior screen uniformity but we wished they packed one more HDMI input in to it, instead of the three ports we have an offer.

    Like just about everyone else, Panasonic ships a choice of two remotes with their Smart TVs. The standard one is fine, if a little outdated looking, but the other gives you the opportunity to test out voice commands and searches – the latter of which works really well. The Smart TV platform, itself, has two notable additions in Freetime and myStream, bringing all the major UK catch-up services and a personalised scrolling screen of recommendations with them, respectively.

    It wasn’t just with the Smart TV functionality where the AS640 performed, however. This TV has it where it really counts – in the picture quality department. The 48AS640 is blessed with a panel boasting great contrast performance, natively, and also a very decent local dimming system which improves it still further.

    Once calibrated, colours were supremely accurate in the True Cinema mode - not that they were bad without adjustment – and the generally excellent screen uniformity meant we could enjoy the pictures on offer more or less free of distraction. There is a bug that means you’ll need to make sure IFC is set to ‘Min’ when watching any content sent at 50Hz but since it’s on by default, it’s not something many will come across. The Panasonic AS640 is just as good in 3D, also, with the active shutter technology providing images that really stand out.

    At its current asking price of £750, the 48-inch Panasonic AS640 is a really good buy as it’s a great all-round TV. Once, or if, the price heads back up north to its suggested retail of £1,000, it starts getting in to tougher competition but it would still come Recommended.

    Suggested retail price when reviewed: £1,000.00

    The Rundown

    Contrast/Dynamic Range/Black Level


    Screen Uniformity


    Colour Accuracy


    Greyscale Accuracy


    Video Processing


    Picture Quality


    3D Picture Quality


    Sound Quality


    Smart Features


    Build Quality


    Ease Of Use


    Value for Money




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