LG PK790 (50PK790) Plasma TV Review

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Finally Phil gets to grips with LG's mid-range 2010 Plasma TV...

by Phil Hinton Apr 6, 2011 at 12:00 AM

  • TV review


    LG PK790 (50PK790) Plasma TV Review
    SRP: £1,100.00


    It seems like an age has passed since the PK series of Plasmas were released in the UK by LG. It must be a good 12 months since the model we have here for review today was first seen in shop windows, yet it has taken a while for us to fully cover this TV on AVForums. Why? Well a number of unfortunate issues managed to get in the way of this review seeing the light of day, the most unfortunate saw one sample destroyed by a careless courier. But finally here we are with the finished review of the 50PK790 and just in time for the sales discounts before the new models hit in the next few months. So is this screen a bargain that shouldn’t be missed?

    Design & Features

    There is one thing that LG always manage to do right and that is TV design. They don’t rely on a conservative design philosophy, where non-offensive black gloss finishes and straight rectangular boxes are all the rage. Nope, that is just not LG’s style these days and the PK790 offers a number of design features that should turn a few heads on the showroom floor. First of these is the one sheet of glass design, which is fast becoming an LG trademark. This approach gives the PK790 a sleek profile with no bezel edges protruding between the panel and the screen edge. The panel chassis is also relatively thin for a plasma TV which adds again to it’s designer appeal, especially when compared to the competition it is up against. The only drawback to this glass approach is, of course, reflections of light bouncing from the front of the screen, so room placement will be important.

    Moving around the back of the PK790 and we are met with what should be considered the bare minimum of source input connections on a modern flat panel. Here we have 4 HDMI inputs along with one Scart, component, VGA/PC as well as a LAN connection. There is also an RS232C port and on the side of the TV we have two USB2.0 slots. So connectivity will not be a problem for the vast majority of users.

    Next up is the remote supplied with the PK790 and we start to see where some costs have been cut. Whilst this is a well laid out design from LG and is logical and easy to use, the feel of the remote is undoubtedly cheap plastic. With the PK790 being aimed at the mid-end of LG’s 2010 plasma range we find this little cost cutting exercise understandable, if a little disappointing.

    Where the PK 790 definitely scores highly is with the introduction of a Freeview HD tuner as well as LG Netcast networking and SD card slot playback. All of these features are just as relevant in 2011 as they were last year, so if you decide to go with this 2010 vintage Plasma you will not be missing out on that many new features. And if you want the new 2011 Smart TV software this can be added via the Smart TV upgrader box, which will be a separate accessory this year.

    Menus & Setup

    As we have come to expect from LG these days the PK790 has the now familiar suite of user friendly menus that really are a doddle to use. Plus we also have the advanced set of menus that will allow control over the TVs video processing and picture set up. These advanced menus are certified by the Imaging Science Foundation (ISF) and the only gripe we have here is the lack of a full 3D Colour Management System (CMS). The CMS here is strictly 2D which means control over luminance of the colours is not covered fully. More on that later.

    The menus are logically laid out and follow the normal workflow of a calibration so advanced users will be able to walk through the set up fairly quickly. We again get a full multi-point Greyscale control which makes fine tuning of the greyscale possible. Again there are some areas we would like improved such as a manual Gamma set up menu, but what we have available here will not affect the vast majority of users.

    One feature that does get overlooked on the LG line of TVs is their picture wizard set up tool. This is an excellent (and accurate) way for end users to set up the Brightness, Contrast, Colour and Sharpness controls without hunting for test patterns, as the system provides them on screen for you. This is the best implementation of this kind of set up walk through program we have seen and it should be used by all owners to get the TV set up correctly for your room.

    Test Results

    In this section of every review we measure all the various picture set up options to find the most accurate to the industry standards for watching TV and Film Material. On the PK790 we have two options certified by THX. The first is THX Bright room which is for daytime viewing as the name suggests it does this by offering more image brightness for viewing during the day. This preset is based on the standards but it does bend these slightly to allow for the extra brightness. This is acceptable in a very bright living room environment, but you should switch to THX cinema for all other viewing environments. Sadly the THX mode on LG TVs also lock out the main front panel controls, so users cannot set the brightness and contrast independently for their rooms. We have fed this back to LG and asked for this to be removed, with locks only on the advanced controls.
    We found that THX mode did offer the most accurate as possible settings for ideal movie and TV viewing, but there were a few little niggles.

    Looking at the greyscale first, we can see that while the three colours do track in a uniform manner, blue is 10% too low with red and green tracking 5% higher than our desired 100% tracking point on the RGB Balance graph. What this relates to on screen is a slight yellow cast to images, they are just a tad too warm. Also the most important measurement for visible errors, DeltaE, shows that we have errors higher than our desired low point of 4 or under. This means that there are visible errors in the greyscale as above with the yellow cast. Gamma is not manually selectable in THX mode and has quite a strange ‘S’ like curve with the higher end of the curve losing luminance down to 2.4, this is strange to see but on-screen the error was very difficult to spot. In fact the effect offers a punchy look to the image with plenty of shadow detail low down, but with a slight luminance shift in the lowest areas. Blacks are not this panels strong point and the added brightness at that end from the gamma is unfortunate but not a disaster.

    Moving to the colour gamut, we are looking for the TV to match the Rec.709 HDTV standard here which should see the colour points line up with the boxes at the edge of the Rec.709 triangle in the CIE chart. Here we find some of the short comings of the PK790, which are not major errors, but are just short of what we are ultimately looking for. Red has a hue and saturation error added to slightly high luminance which is the most major of the errors seen. There are errors with the secondary colours, which we may be able to improve slightly when we calibrate the greyscale. This is not that bad of a chart given some other HDTVs we have tested, but we can maybe balance out some of the more major issues and keep luminance in check. This is important as a high luminance will override the saturation and hue settings.

    Overall, the THX mode on the PK790 is not as accurate as similar presets on other TVs we have tested, but it will give users the most accurate greyscale and colour performance available without a professional calibration.

    With the PK790 featuring a 20 point greyscale option, we used that to fully calibrate the panel to gives us error free grayscale tracking. As you can see in the RGB balance chart, we were able to get every point of the greyscale perfectly balanced with DeltaE errors well under 1. Gamma also tracked quite a bit better after correcting the greyscale, however there was nothing we could do to move the error around 90IRE which is a slight annoyance, but not really noticeable when watching content on the TV. Overall this is excellent performance.

    As explained above, we could have left the CIE results close to where they were in the out of the box measurements. However, with the corrected greyscale this brought the secondary colours back to where we would like to see them. There are still errors here, but what we tried to do was balance the results out so we had acceptable luminance levels and other errors in check. This provided pretty good accuracy, on screen, and we would be astonished if any viewer would be able to see the small errors here (unless there was a side by side comparison with a reference screen). Overall, given the price point and performance of the panel here, we were very happy with the end results.

    Picture Processing

    One of the reasons we took so long with the PK790 review was the fact that it did have a bug with sharpness being added behind the scenes to HD material. Thankfully this is now a thing of the past, with the 790 producing excellent HD images with no forced sharpening going on.

    We fully tested the PK790 with our vast suite of processing tests and with SD material the LG managed good scaling of the image with no obvious ringing or haloing to edges. Images, depending on the source were fairly sharp and well detailed with only heavily compressed DTV channels looking a little ropy. Motion resolution was also very good in SD and HD with solid lines on Football pitches with no signs of image break-up. 24p was also handled correctly with no signs of induced judder from the PK790.

    Input Lag

    Gamers out there can probably pass on the PK790 which returned an estimated lag time of over 45ms. This is rather high for the competitive player and it was roughly the same result in all picture modes.

    Power Consumption

    As the PK790 is a plasma screen it has a varible power consumption depending on the picture modes used and the material being viewed. We measured 135W with a 0IRE pattern, 267W with a 50IRE pattern and 310W with a full white screen. Remember these are static test patterns and in a half hour viewing session in calibrated mode the LG averaged 240w peak.

    Picture Quality

    The one area where LG screens have fallen down slightly in the past is with their black levels and sadly it is no different here. The screen filter on the LG is not as good as the 2010 Panasonic versions so the LG does lack behind the competition slightly in this regard (but the LG also doesn’t exhibit some of the picture traits of the Panasonic models either, such as 50Hz breakup). I have heard some forum members state that some LCDs out there can better the LG in terms of absolute black, and they would be right to a degree in some cases. However, where the PK790 does perform well is with detail just above black adding a sense of depth that many LCDs would struggle with. When watching normal TV programs and films (rather than a black screen) you soon forgive the LG slightly for its lack of absolute black when you are greeted with good motion resolution and very accurate greyscale and colour performance. It is a trade off on the LG, but some will say that at the price point you can now pick up this 2010 TV, it is a worthwhile trade.

    So, overall the only slight let down is the lack of absolute black level performance which is not as deep as much of the competition, but more importantly everything else in the image (when set up correctly) is appealing for the money spent, with strong motion and colour performance. HD images are also now super crisp without added sharpening behind the scenes. Obviously if you are a discerning consumer with a love of films it usually falls to a Plasma for the filmic image with good shadow detailing. The LG does this to an acceptable standard but that lack of overall black level performance (which is more dark grey) might put you off slightly. As an everyday multi-use screen, however, the LG does well and at the prices it is now available at, a bit of a bargain for some.


    OUT OF


    • Excellent menu system
    • ISF and THX certified
    • Excellent colour accuracy when set up correctly and in THX mode
    • Excellent Greyscale tracking
    • Motion resolution


    • Average black level performance
    • Cheap remote
    • Image retention is visible with heavy use of channels with graphics or gaming
    • Average sound quality
    You own this Total 0
    You want this Total 0
    You had this Total 0

    LG PK790 (50PK790) Plasma TV Review

    The PK790 offers many of the plus points of owning a plasma screen, and as this is an out-going 2010 set, it does so at very competitive pricing. It has a good selection of features including THX and ISF certification, DLNA, Netcast and a freeview HD tuner. It also boasts the now familiar and excellent picture wizard for normal mass market users to set up the main controls correctly for their viewing room. The other strong point is also the design of the TV, which rather than being a black rectangle, it has the very nice one sheet of glass design and thin bezel and cabinet depth.

    Where things start to go slightly wrong is with the black levels of the image, which are not as deep or fluid as some competition, including some of the best LCDs out there. But then again, those TVs are also far more expensive than what is on offer here with the PK790. So dark grey blacks are the order of the day here, but everything else in the image is also very appealing when set up correctly. Colour accuracy and greyscale tracking is very good and if you can’t stretch to a full calibration, the THX Bright and THX Cinema modes fulfill the day and night options fully and to a high enough standard for the mass market user. Image retention can be an issue with long term viewing of images with heavy graphics or with gaming. However this should disappear over time naturally. I only found it slightly annoying on about two occasions in my two months of viewing on the PK790.

    Overall, the PK790 offers an appealing set of features and a decent stab at image accuracy and blacks. It is not the best, by far, in that department, but as an all-rounder - and at the now reduced pricing it is available at, it is perhaps worthy of your attention in a demo.

    Suggested retail price when reviewed: £1,100.00

    The Rundown

    Contrast/Dynamic Range/Black Level


    Screen Uniformity


    Colour Accuracy


    Greyscale Accuracy


    Video Processing


    Picture Quality


    Sound Quality


    Smart Features


    Build Quality


    Ease Of Use


    Value for Money




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