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Picture Quality On TH42PX70

by Colin Tang
21 March 2007

Now with the Panasonic Plasma TH42PX70 up and running for at least 200 hours, we're ready to proceed to our next stage. As I said earlier, you are presented with three viewing options at the setup screen: dynamic, standard and cinema. You can be 'dynamic' employee of the month or have a 'dynamic' personality, but trust me, when it comes to TVs you're best to avoid it like the plague. Unless, of course you like looking at the sun, enjoy Smurf-like skin tones or colours from an over-enthusiastic artist's pallette and like having your images encased in angelic haloes.

Try my sand-on-the-beach-on-a-bright-afternoon-day scene test to see what a simple change in colour temperature can do alone. With two flicks at the remote, the warm, cinema mode gave us first impression pictures the Oscars would have been proud of. Calibration has never been this easy.

Torture Test

Dead pixels Passed
Screen Uniformity Uniform
Overscanning on HDMI, Component 2.5 percent
Blacker than black Passed
Black level Find out below :)
Black level retention Unstable
Primary chromaticity Fair
Scaling Fair, soft scaling
Video mode deinterlacing Fair, limited jaggie reduction
Film mode deinterlacing 3:2 reverse only with poor lock
Viewing angle Excellent
Motion blur None
Digital noise Not noticeable at 8 feet
Sharpness Defeatable edge enhancement

Black Level

Black level
This scene's black level test is unforgiving!

Panasonic had a black-level reputation to keep with this new G10 panel, and not only does it do that effortlessly, it rockets straight to the top and joins the party with its predecessors. This is, hand on heart, probably the strongest reason why you should consider getting this TH42PX70 plasma panel. I had some friends over the weekend (32 and 37 inch LCD owners) to look at the TV and so I put on a black level busting test, Unforgiven and let them soak up all its glory. There was, as you may expect, universal praise and some expletives thrown about for good measure because of the deep but detailed blacks in those scenes.

The TV passes blacker-than-black levels and so you can be confident about calibrating reference black level accurately. For reasons I don't understand, the black level retention tests were unstable, meaning that the black part of the screen fluctuates depending on the average brightness of the current image. There was no dynamic dimming function in the user menu to turn off. The good thing is that it is done very discreetly and was not noticeable on regular viewing.

Dynamic Contrast Ratio

Post calibration dynamic contrast ratio was an impressive ~1000:1 due to the excellent black level. Furthermore, the Panasonic TH42PX70 had enough contrast (white level) to encourage flexible all-day viewing, something which LCD had a distinct advantage over plasma displays previously. Images are rendered with a lot more depth and wider tone scale.

Greyscale

Gamma CCT
Greyscale graph at gamma 2.20
The dotted blue line shows 6500K at 0 to 100 percent stimulus

We couldn't improve on the Panasonic's initial offering of greyscale characteristics on Warm, Cinema Mode. You get a gamma of 2.2 with a smooth greyscale intensity curve and a CCT graph very close to the D65 standard at all intensities. All this at a healthy contrast level setting and 1000:1 contrast ratio without lifting a finger! If all TVs came like this, some of us might be out of a job soon...

Colour

CIE
Greens a bit more saturated and bluey with yellow having an orange tint

The Panasonic TH42PX70 comes with a 'footie colourspace' with its primary green a little accentuated and a little more towards blue. This gives football fans something to cheer about when the pitch looks 'spot on', 'resurfaced' or like new. Subjectively, the greens are a little more saturated than say the recent Pioneer PDP4270XD, but it's nothing you'd be disappointed with. Green push is infinitely more tolerable that say the more common but dreaded red push.

Motion

Motion handling on a plasma screen is always top notch and while it may not directly compete with a high refresh rate CRT, it does wipe the floor with LCD screens of average response times.

Detail and Sharpness

It is a mathematical fact that any 1080p material downconverted to a 1024x768 display panel will lose some detail from the original image. But I suppose the question is, can you really 'detect' the loss of detail? Personally I can't and I bet the same goes for many viewers as well. Don't get me wrong; nothing would please me more than having the latest true 1080p plasma panel but I'd wager that it's gonna do the high circuit before it comes down to an affordable level.

The scaling on our review model couldn't match our upscaling Toshiba HD-E1. The pictures were softer as a result, but with no excessive ringing or jaggies. Some overscanning is expected with normal programme material.

Overscan
About 2.5 percent overscanning was present on HDMI and component connection.

Viewing Angles

I have yet to see a well designed plasma screen fall short of expectation on this, and I hope I never will.

Video Artifacts

Purple snake   Greyscale
?Purple snakes
 
Greyscale with magenta bands

We knew about the main problems that caused some sleepless nights with previous Panasonic owners' and so we were on the lookout for it. First off, several discrete magenta bands were present on smooth greyscale ramp at about 30-50 percent stimulus. This is manifested as purple bands on grey, green or brown smooth gradients found in SD or HD programmes. The effect is very mild and after hours of viewing I could only confidently detect the bands on a handful of material.

The second issue worth noting is the appearance of posterization or false contouring seen on certain scenes. The recently reviewed Pioneer PDP4270XD was better in this regard. They appear as steps of different colour luminances in smooth gradients. It is very difficult to isolate specific causes of posterization in our case but it is clear that poor quality of material tends to make the problem more pronounced, although this effect has also been seen on HD sources.

Shimmering pixels and colour trailing (yellowish green) behind moving high-contrast images are seen. They are inherent to current plasma technology and may alienate some users who are especially sensitive to the effects. From 8 feet, general image noise was not an issue.

The Panasonic TH42PX70 didn't do too well in our robust deinterlacing tests. While it prevented major combing defects in video mode deinterlacing, it didn't have advanced directional jaggies filtering. On some scenes, mainly in SD because of the lower resolution, twitter, jaggies and moire patterns creep into your viewing experience. It might have ruined it were not for the Panasonic's overwhelming strength in basic picture quality aspects.

The Panasonic panel only has a built in 3:2 cadence detection but it fails to lock on to film material very effectively, causing some of the above artifacts. If possible, I would be tempted to outsource the film and video mode deinterlacing to external processors with the right budget.

High Definition

Harry Potter   Voldemort
I'm a fish... Harry Potter 4
 
Voldemort with a death curse
Dirty Harry   Dirty Harry 2
Dirty Harry in Unforgiven...
 
Are you talking to me?

With HD sources, the picture quality of this set leaves very little to be desired when you consider its price-performance ratio. The wonderful thing is that it hits the mark with basic picture quality components that we value highly. The inky, hypnotic blacks bestowed images with a 3-dimensionality that is hard to equal, much less beat. Shadow detail was expertly conveyed to the viewer with no hint of dark screen fog that besets lesser TVs.

Despite the low panel resolution, the image is still smooth and sufficiently detailed to guarantee your viewing experience. Colours, though slightly off on objective measurements, appear balanced and handled delicately, thanks to its superb contrast ratio, greyscale tracking and colour temperature.

Sure, I made a long list of artifacts above but the increased resolution of HD material tend to 'cover up' these problems fairly well. One thing I didn't do was jump out of my seat whenever some artifact came along. I was so locked into the picture most of the time that only a giant purple snake could have broken my attention.

Standard Definition

Toy Story   Toy Story
Toy Story
 
Toy Story...Woody and Buzz
Arwen   Bugatti
The elfin Arwen
 
Bugatti Veyron

What's the quality like for SD stuff? I have been getting many questions from readers concerning this and understandbly after parting with all that cash for a high definition TV, you may be forgiven for expecting a decent performance with standard definition material. Without going into too much detail, the essential problem is that low resolution, interlaced, MPEG-artifact infested digital SD source is being displayed on progressive, large screen HDTVs that are really built for HD source. The same basic PQ standards still apply to the two types of source but in addition, you may need to consider the effects/artifacts caused by TV scaling, deinterlacing and MPEG noise reduction.

For basic picture quality, the Panasonic TH42PX70 is still very strong in the usual departments ie blacks, contrast ratio, motion handling, viewing angles and colour balance – and that's something we don't expect to change drastically with different sources. Colour accuracy and saturation do change with SD source because of chroma subsampling in MPEG-2 and different colour encoding.

Most complaints about SD material on HDTVs come from softness and artifacts from lower quality scaling, deinterlacing and MPEG noise processing. For this Panasonic panel, the quality of scaling, as noted, was inferior to our Toshiba HD-E1 upscaling player, which happens to be quite decent. This caused the image to be blurry on comparison. The average deinterlacing caused twitter, jaggies and moire patterns on a few programmes and movies, which I have no doubt will annoy some discerning viewers. Mosquito noise and the occasional blocking will be seen on fast action SD material; the display only has what seems to me to be a mild 2D spatial filter for MPEG noise removal that I don't particularly recommend.

The fact of the matter is that you will be paying top dollar to get the best looking SD material, considering the advanced processing that is available out there. However, the good thing is that you can actively remedy the situation by attacking specific 'weaknesses' of the Panasonic TH42PX70 by outsourcing the scaling and deinterlacing processes to external units. There are many DVD players and freeview set-top boxes out there with higher quality scaling chips that you can consider. Some DVD players may have superior film mode deinterlacing capabilities and it won't be long before we get a 1080p upscaling DVD player. But in the end, true SD nirvana may only be experienced by users with dedicated external video processors.

Panasonic TH42PX70 Settings

The following settings are calibrated for HD broadcast and HD DVD performance via HDMI input in a dark viewing environment. There are several reasons why they won’t work for you, as they can all affect `final’ picture quality.

  • Personal preference
  • Ambient light
  • Source material
  • Player
  • Intramodel variation

Picture Menu

Viewing Mode: Cinema
Contrast: No change
Brightness: 2 clicks left
Colour: No change
Sharpness: No Change
Colour Balance: Warm
Colour Management: Off
P-NR: Off

That was easy, wasn't it? I tolerated a small degree of edge enhancement to counter the softness of the internal scaling. For football in SD broadcast or whatever else you fancy, you can turn on Colour Management for deeper greens. Happy viewing guys.

Back To: TH42PX70 Review

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