Panasonic Viera TX-P42GT20

For the start of the new year, Panasonic is adding more 3D plasma TVs to its collection, including this new 42'' GT20. 

It's being billed as a 3D version of the G20, which we awarded four stars in our recent review.  Apart from adding 3D Ready support, the two TVs share the same features and components, including a NeoPDP Full HD plasma with Infinite Black technology, although it isn't the Pro version of this filter found on the V20 and VT20.  There's also a built-in TV tuner, and a 600 Hz SFD filter with 24p Real Cinema, the equivalent of Motion Flow and Motion Plus from Sony and Samsung respectively.

These filters improve the fluidity of fast-moving objects on screen to reduce the jerkiness caused by the 24 fps framerate used in films.

3D Glasses



To get the full 3D effect, each viewer will need a pair of 3D glasses compatible with this TV.  Unfortunately, as is so often the case, the GT20 doesn't come with any.  That means you'll have to buy a pair to get the most out of it: they cost £92 each.

At that price, we'd expect some pretty decent glasses.  However, we still prefer Samsung's which are rechargeable and cost £40-60 a pair.  Panasonic's main problem is the rigid arms which grip very tightly, especially if you've got a big head.

Panasonic adds 2D to 3D conversion

Panasonic initially decided not to include 2D to 3D conversion in its first 3D TVs.  At the time, the manufacturer's argument was that conversion wasn't 'yet a mature technology,' claiming its 'VT20 is a very capable 3D Ready television: what it does do, it does well.'  Now, though, Panasonic seems to have come round, following widespread demand from consumers.

Unfortunately, it seems that the addition of 2D to 3D conversion has been rather rushed, and the results don't match up to what we've come to expect from Panasonic.  When 3D effects are visible, they're hardly stunning, with a few objects leaping off the foreground every now and again.  It's a shame, as the only real benefit is that Panasonic can add conversion to the feature list.

3D Quality and Problems

Unlike the 2D to 3D conversion, the results produced by 'real' 3D from a Blu-ray 3D disc is of excellent.  Objects leap out of the screen and there's a real depth of field.  Better still, there are some real advantages to using 3D technology on a plasma screen instead of LCD.

To understand the advantages, we used the test card above in side-by-side 3D mode.  The frame is cut in two, with the left-hand side shown to the left eye, and the right-hand side to the right eye.

These are the results seen through the glasses, Panasonic on top, and Samsung below:

Panasonic's 3D plasma TVs are less affected by crosstalk than the Sony HX803 or the Samsung C7000 and C8000, but the results still aren't quite pefect.  Some of the feed for the right eye is visible to the left eye and vice-versa.  For example, the large 'L' is almost invisible on the 'R' half of the card.  This defect is most noticeable on light objects set against a dark background.  In the opposite case (dark objects on a light background), the problem is much less visible.

A second problem if one that affects all 3D TVs: a large amount of brightness is lost when you don the 3D glasses.  After a series of tests, our tests revealed a drop in brightness of 70%.  Given that plasma screens aren't too bright to start with, you have to make sure you have a dark room for your 3D films.

Build Quality and Design

Let's get one thing clear, looks really aren't Panasonic's strong point.  The manufacturer has certainly been working hard to cram the features into its new TVs, but we rather get the impression that the design for its 2010/11 collection hasn't been updated for several years.   As well as being one of the thickest TVs we've seen at 8.2 cm, the GT20 as a wide black frame that's too big and a rather ordinary-looking round stand.  Equally disappointing was the remote control, which is beginning to look dated and has a very old design with no backlighting.

Despite Panasonic's best efforts, the glossy panel over the screen is still very reflective.  You'll need to be careful to keep the TV away from direct light sources.

Other features include built-in video-conferencing using Skype, as well as the best of what Panasonic had to offer last year. That means four HDMI inputs, Internet connectivity for accessing online features, motion blur reduction, THX certification and a media player. This last element is pretty disappointing as it doesn't support NTFS, so you're stuck with external peripherals formatted as FAT32 and a very limited range of file formats.

Built-in PVR

Like the G20, the GT20 can act as a digital TV recorder. Once you've plugged in some storage, like a USB key, it can be formatted to store recordings of TV programmes. During this process, it's tied to your TV with DRM to avoid the possibility of using the system to share files illegally.

Responsiveness: 15 ms for LCD panels, 8 ms for the GT20 plasma

We recently started using a new test for responsiveness in our lab.  We now time how long it takes for the previous frame to disappear completely from view, and use foregrounds and backgrounds of several different colours.  The longer it takes, the more subject the screen will be to ghosting, which will leave fast-moving objects looking blurry.

We used it on the latest PVA and MVA LCD panels, and both produce an average response time of 15 ms; remember, the shorter this time, the better.  It takes these TVs 15 ms to completely clear the previous frame.  To put it another way, that's 15 ms during which an object looks like it's in two places at once.

With the same test, the Panasonic GT20's response time was almost twice as fast at 8.5 ms.  That's incredible: this Panasonic plasma is almost twice as reactive as its LCD rivals.

Image Quality: Factory Settings

By default, TVs ship with settings that are designed to create a strong impression on new viewers, but it's a totally false representation of the video source.  The GT20 was no exception to the rule, and has inaccurate colours, with a very strong blue tinge, and an uneven luminance curve.  Overall, we were very disappointed.


Image Quality: THX Mode

Fortunately, switching to THX mode radically improves things.  The only small problem is that we found the picture too dark for everyday use.  We suggest that you turn the contrast up once the TV's had time to warm up.  But even at the maximum setting, whites don't climb over 180 cd/m² on an average test card (25% white).  That means your TV will be lacking a little oomph in very bright rooms, so think twice about it putting it in a south-facing room on a sunny day.  On the other hand, the viewing angles are, of course, absolutely excellent, as is usually the case with plasma TVs.  The GT20 also has a great contrast ratio, with an average of just over 2600:1.


Colours are reproduced much more naturally in this mode too.  Our equipment indicated an average deltaE of 2.1, which is an excellent result.  Remember that we usually consider that any remaining discrepancies are invisible to the naked eye when this value is below 3.0.

In THX mode, IFC is turned off by default.  When you switch it back on, it largely compensates for the jerkiness introduced by the 24 fps framerate used in films.  The downside is the addition of visual artefacts around fast-moving objects.  The overall quality, remains, however, excellent.

As with most TVs, native HD content is perfect, but upscaling of SD content can be a bit blurry.  We suggest you leave the job to an external source like a DVD player, Blu-ray player or your PS3 rigged up to a HDMI port.

Audio Quality

The sound produced by the GT20's speakers isn't up to the picture shown on screen.  Bass is almost entirely absent, although the mid-range and treble both make a decent case.  To improve on the 2 x 10 W speakers, we can only (once again) recommend you go for an alternative, like a Home Cinema speaker system or a sound bar.

Energy Consumption

Finally, let's look the dark spot on this television ... and plasma screens in general: the amount of power they need!  While it's minimal on standby (0.1 W), it's huge when you turn it on: we noticed an average consumption of 222 W.