Note: Our Panasonic TX-P50VT50B review sample was calibrated using Calman Professional, the industry-leading video calibration software.
|Pre-calibration RGB tracking and delta errors (dEs)|
We selected the [THX Cinema] mode, and ran a series of Greyscale tracking measurements to see how tint-free the TX-P50VT50′s grey shades were before any in-depth calibration. Although our meter reported inaccuracies (too much blue), we were pleased with this for two reasons. First, for an uncalibrated consumer Plasma TV, the tracking is very uniform from the darkest to the brightest measured levels (10 to 100). Secondly, previous Panasonic plasmas have shown a green tint in their pre-calibrated state, which had a more detrimental effect on overall image realism than a slightly blue one.
In fact, after we did a full calibration and switched back and forth between calibrated and out-of-the-box settings, we were surprised at just how small the difference was. This served as a stark reminder of the fact that, if you’re stuck with less-than-perfect Greyscale tracking, some excesses are better than others. We would happily watch the Panasonic TX-P50VT50B in its THX Cinema mode without calibrating it based on the performance we saw. That’s not to say that VT50 owners shouldn’t consider calibration, of course: this varies from one set to another, with individual units and the number of hours they’ve been used for all contributing to how good greyscale tracking will be.
Since we have the option available to us, we used the [Professional] mode’s calibration controls to push the Panasonic TX-P50VT50 to the limit, and see it at its maximum potential:
|Post-calibration RGB tracking and dEs in [Professional1] mode|
First, we used the standard 2-point [White Balance] controls, which let us adjust the low end (darker areas) and high end (brighter ones) for a highly accurate image. That resulted in visually perfect grey shades, except for the 10% stimulus area: shadows were showing a red tint. So, we used the 10-point controls (tucked away in a menu called [More detailed adjustment]) to level out the remaining imperfections. That process went well, but during our adjustment of the 10% stimulus, we noticed that a quirk from last year’s displays was still present (albeit to a lesser extent): bringing up one of the on screen menus will cause a slight shift in greyscale tracking, which isn’t hugely obvious to the eye, but is revealed by a meter. That suggests largely excellent, but slightly unpredictable performance outside of test patterns.
With real-world content, we still saw some slight red tinge at around 5% stimulus (not visible on the above Greyscale tracking chart because we measure it in 10% stops). This was very subtle, however.
|Gamma curve in [Professional1] mode||Corresponding gamma tracking|
Gamma tracking describes the amount of light output by the TV screen relative to the levels in the video signal. If the gamma is too low, the image will appear washed out. If it’s too high, details in dark areas will be hard to see, or perhaps even be missing entirely. And, if it’s a more extreme mix of the two, the image will look unnatural.
Unlike most Panasonic Plasmas, the “2.2″ gamma setting on the TX-P50VT50B actually gave us 2.2 gamma tracking, which is the setting that’s best for a normal viewing environment. (In fully darkened cinema environments, a higher gamma setting of around 2.4 or 2.5 is often recommended, due to the way that our eyes adapt to darker viewing environments).
Normally we have to select the “2.4″ option to actually get 2.2 out of a Panasonic Plasma TV, so this is a welcome improvement. After Greyscale calibration, we were left with highly accurate gamma tracking measurements, with only a slight over-emphasis of dark areas (10% stimulus), and a slight dimming at 80% stimulus standing in the way. Panasonic offers a 10-point gamma calibration control, too, so we were able to get a perfectly flat 2.2 response during our test measurements – meaning that the Viera VT50 was outputting each intensity level with exactly the right amount of brightness.
Of course, as with all of the consumer Plasma TVs we’ve recently looked at, it’s not that simple when it comes to real-life performance. The actual gamma (and greyscale) performance varies depending on the picture contents being shown, with rock-solid-accurate results only being delivered by content that shares a similar overall brightness level as the test pattern used during the calibration. To give you some idea, the perfectly flat 2.2 gamma which we lined up with windowed test patterns came in slightly more curved and closer to 2.4 when we measured it using the APL patterns from the same test disc. We didn’t find the inaccuracy troubling at all when watching the TV, but it is there.
You might note that there is a small dip downwards on the “Gamma Y” tracking chart (above right). If we have full control over this, then why didn’t we obliterate that entirely? Because pushing the 10% stimulus gamma adjustment can actually re-introduce “floating gamma”. That’s where the TV can shift the tonal distribution of a scene can slightly as it’s being viewed. We saw this on the corrected version of the VT30 series last year (the original system software had a more severe case of “floating gamma”), and also found that with that model, we could avoid the problem entirely by sacrificing a little bit of gamma accuracy. The effect was incredibly mild on the Panasonic TX-P50VT50, and again, we went back and eased off the 10 IRE adjustment a little after our first calibration, which cured the barely noticeable problem without significantly affecting accuracy.
As we’ve come to expect from post-2009 Panasonic plasma products, the Panasonic TX-P50VT50B has no significant colour errors before, and especially not after, calibration. In the [THX Cinema] mode out of the box, we could only count a slightly too orange red and a mildly oversaturated green as measurable, and barely visible, errors.
Panasonic gives full control over every aspect of colour reproduction on the TX-P50VT50, so it would be pointless for us not to fine tune things to perfection for the purposes of reviewing the VT50 operating at its peak. However, we would happily have watched it without complaint if we, for some reason, were unable to fully calibrate colour. Here are the calibrated results, all of which result in an on-screen image without any obvious errors.
|Post-calibration CIE chart with reference to HD Rec.709|
|Post-calibration colour luminance (coloured bars = targets; black bars = measured values)|
One interesting thing to note regards the consistency of the colour luminance levels. On nearly all Panasonic Plasma televisions we’ve calibrated, we’ve found that adjusting the luminance levels with windowed test patterns makes actual programme content look dull and washed out, due to the unpredictable gamma performance we mentioned above. On those Plasma HDTVs, we had to instead use an APL test pattern during the calibration in order to get good real-world results. Although there were still differences in colour luminance levels when measuring with the two sets of patterns, it was not as pronounced on the Panasonic VT50, suggesting that some improvement has been made here.
3D calibration isn’t widespread, and that’s a shame, because the improvement it makes to tri-dimensional imaging is just as important as it is for 2D – moreso when we remember that Plasma TVs in particular often have less accurate Greyscale tracking in their out-of-the-box 3D modes. We selected the “THX 3D Cinema” option on the TX-P50VT50B, and then measured 3D Greyscale tracking patterns with one of the supplied pairs of active-shutter glasses attached to the front of our Klein K-10 meter.
|3D Pre-calibration RGB tracking and delta errors (dEs)|
Pre-calibated 3D greyscale tracking was similar to last year’s TX-P50VT30. Remember though that the greyscale characteristics of each pair of glasses is slightly different (we used a pair of the bundled glasses in each case). Shadowed areas had an excess of blue, although we didn’t feel the result was hugely damaging given the other pitfalls that can occur with extra-dimensional images. Greyscale tracking shifts over time, so it’s possible that after 200-300 hours or so, the TX-P50VT50′s THX 3D Cinema mode will be more accurate.
|3D Post-calibration RGB tracking and dEs in [Professional1] mode|
The 10-point Greyscale control is also available in 3D mode, so we adjusted the 2-point controls to achieve the flattest possible greyscale tracking to start with. That meant that 40-100% stimulus were more or less correct, but we still had too much blue at 10-30%, something we corrected with those specific controls.
Colour reproduction in 3D was nearly identical to 2D, with a mild saturation error in red and blue being the only measurable (but not really visible) inaccuracies.
|3D Post-calibration CIE chart with reference to HD Rec.709|
|3D Post-calibration colour luminance (coloured bars = targets; black bars = measured values)|
Benchmark Test Results
|Screen uniformity||Excellent, no colour or brightness impurities noted|
|Overscanning on HDMI||0% with [16:9 Overscan] set to “Off“|
|Blacker than black||Passed|
|Calibrated black level (black screen)||0.009 cd/m2|
|Calibrated black level (ANSI checkerboard)||0.012 cd/m2|
|Black level retention||Stable, but care must be taken with 10 IRE setting in 10-point Gamma control to avoid introducing very subtle “floating gamma”|
|Video mode deinterlacing||Very effective jaggies reduction|
|Film mode deinterlacing||Failed 2-2 PAL film mode test, 3-2 NTSC passed|
|Viewing angle||Excellent, screen filter blocks ceiling lighting, so vertical viewing angle lessened. Screen filter can cause streaks to be visible through 3D glasses when screen viewed off-angle|
|Motion resolution||Excellent (1080 lines)|
|Digital noise reduction||Present, optional|
|Sharpness||Subtle undefeatable high frequency sharpening, see notes|
|Luma/Chroma bandwidth (2D Blu-ray)||Full Luma, Full chroma with a 4:2:2 HDMI input, or with the [1080p Pure Direct] mode turned On otherwise|
|Image retention||Very little, clears quickly|
|Posterization||Very small “hardened” edges during fast motion|
|Phosphor trails||Mild, some red trailing noted, may change with age|
|1080p/24 capability||No judder in 2D or 3D|
|Input lag||Excellent: 24ms compared to lag-free CRT|
|Full 4:4:4 reproduction (PC)||Yes, only with YCbCr signal type, not RGB, some subtle “ringing” artefacts present on highly saturated transitions due to edge enhancement, see notes|
|Default [Normal] mode (2D)||317 watts|
|Default [Normal] mode (3D)||281 watts|
|[THX Cinema] mode (2D)||224 watts|
|[THX 3D Cinema] mode (3D)||266 watts|
|Calibrated [Professional1] mode (2D)||189 watts|
|Calibrated [Professional1] mode (3D)||266 watts|
|[THX Bright Room] mode (2D only)||382 watts|
Measurements taken with full 50% grey screen to approximate real-world viewing.
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