Picture Quality in Detail

The ultimate deciding factor for a flat-panel TV is, of course, the picture quality. In this chapter, we'll describe in detail how well the LG 42 LH 7000 really performs in terms of contrast, black level, sharpness, and signal processing. We'll also back up our results with measurements from our test laboratory.

Contrast and Black Representation:

This diagram shows the contrast ratio in various picture modes and with various measurement methods.

The LG is clearly no contrast-wizard. Dark movie scenes, in "Kingdom of Heaven", for example, have little depth. Even in the best preset, "Movie", and with our calibrated settings, black areas of the picture look dark blue and are only 1000 times darker than white areas. In the "Vivid" mode, the LG produces around three times as much contrast, but the picture then has a pronounced blue tint.

For comparison: The current best LCD TVs produce an in-picture contrast of up to 3,000:1; the best plasmas achieve even higher contrast ratios. Exceptional contrast can be found in, for example, the Sony KDL-55 X 4500 (an LCD with a sub-divided backlight, using the "local dimming" technique) or Pioneer's plasma bombshell the KRP-500.

Black Level Test:

The black test pattern shows how much so-called residual illumination the TV produces when trying to display pure black; technicians refers to this value as the "black level". Ideally, a black picture should appear perfectly black, but almost all TVs allow a small amount of light to leak through.

Several factors affect the way the viewer perceives this residual illumination: for example, how strongly the ambient illumination brightens up the TV screen (only slightly for LCDs, but rather strongly for plasmas), how high the TV's contrast ratio is, how light it is in the room, and how strongly the intensity of the residual illumination depends on the picture content.

A completely black image still shows a significant amount of light on the LG. In the "Movie" preset, the black level measures 0.22 candelas per square meter (cd/m2). If you activate the OPC function, which reduces the lamp output in black pictures, the black level drops to 0.15 cd/m2.

The LG produces its best subjective picture impression in rooms with a bit of ambient lighting, which should ideally come from behind the TV, since this makes the poor black-representation less obvious.

For comparison: Modern plasma TVs, such as the Panasonic TX-P 42 GW 10 achieve a black level of just 0.04 cd/m2 - in dark surroundings, you see only minimal residual illumination.

Viewing Angle Dependence:

This diagram shows the degree to which the picture depends on viewing angle. In the ideal case, you would be able to see a circle. The more club-shaped the diagram looks, the more strongly the picture quality depends on the viewing angle. Most plasma TVs are significantly better in this respect.

With side-on viewing, the LG's brightness and contrast drop as the angle increases - this behavior is typical of an LCD screen. The color reproduction only changes moderately when you view the picture from one side: The colors tend toward yellow/brown, and the color temperature drops as the angle goes up.

You should therefore always angle the LG toward the viewers, which is easy to do with the help of the supplied swivel pedestal. The contrast drops by half when the viewer moves from a central position to an angle of just 20 degrees from the center.

Video Processing of Standard Signals:

With the "multiburst" test pattern above, we can judge sharpness and fine-detail reproduction in the horizontal direction. Other test patterns, not shown here, allow us to check the sharpness in the vertical direction, and show how finely the TV processes colored details.

Overall, the LG's signal processing is acceptable. Pictures arriving via the Scart (RGB) input, from a satellite-TV receiver, for example, look a little soft, since the TV's display of horizontal and vertical details is less than perfect. In addition, movie-mode detection is not stable for this kind of input signal. In other words, line flicker is visible in tricky scenes: In the camera pan at the beginning of the fifth chapter of the DVD "Six Days Seven Nights", the beach loungers flicker slightly.

The LG displays a significantly better picture via the HDMI input. Even at just standard resolution (576i), the TV displays a well de-interlaced picture with crisp details, and the camera pan across the beach in "Six Days Seven Nights" is clean. The LG displays even trickier scenes accurately, including, for example, the fine picket pence in the eighth chapter of "Space Cowboys", which is a real acid test for every de-interlacer.

Like most competing models, unfortunately, the LG crops the edges of incoming signals to an unnecessary degree; this "overscan" reaches up to 20 percent, depending on the signal. This means the picture gets bigger and its quality gets lower, since less picture information is now forced to fill the screen.

With Scart, the LG cuts around 40 pixels from each side of the picture, and 15 pixels from both the top and bottom (pixel cropping) edges. With HDMI-576i, it still crops around 20 pixels at each side and 10 pixels top and bottom. Only HDTV signals allow you to see the full picture.

Video Processing of HDTV Signals:

The LG displays fine patterns accurately, and the sharpness and degree of detail are likewise impressive with well mastered Blu-ray movies such as the James Bond adventure "Quantum of Solace".

The LG's accurate signal processing impressed in test patterns.

The LG also displays this fruit-bowl test picture accurately. 1080/24p signals from a Blu-ray player are true to the original and show the regular movie judder seen in the movie theater. This is easily seen in the opening to the movie "Casino Royale" as animated playing cards fly across the screen.

With interlaced input signals in 1080/60i format, the de-interlacer works accurately, meaning that fine structures show no flicker - the decorative stripes on the sea-plane in the fourth chapter of "Casino Royale" are a great example of this.

Tuner Pictures:

The analog tuner picture looks natural and shows little graininess, even with the noise filter deactivated. There could, however, be a little more fine detail.

DVB-T gives a sharp and detail-rich picture, but could do with a bit less picture cropping. This would improve the picture quality, making the picture's compression artifacts, for example, less obvious. Modern plasma TVs such as Panasonic's TX-P 42 GW 10 (or TX-P 42 G 10 in some markets) are exemplary in this respect, allowing the user to turn off overscan for digital TV signals.

Picture Uniformity and Digital Picture Errors:

The LG's picture uniformity is excellent: The brightness, color reproduction, and contrast vary only minimally - and never irritatingly - within a picture. Motion clarity is a touchy subject for LCD TVs if objects move across the screen quickly. Cheap LCDs often tend to show blur ("motion blur") on fast-moving images such as tennis balls or details within a camera pan.

The LG is one of the better LCD displays: Its tendency to blur and the quality of its motion depiction depend on its settings. With the backlight turned down, fast objects display clearly but with triple edges; at maximum brightness, the LG tends to blur instead.

With movie material, which contains less motion information than video from the word go (24/25 instead of 50/60 motion phases per second), the picture remains crisp even in fast camera pans. The displays with the best motion clarity currently come from Panasonic; one example we can think of is the TX-P 42 GW 10, but that model's picture flickers slightly.

With video material, on the other hand, the LG shows slight blurring. This gets better if you activate the "TruMotion 100 Hz" setting, which generates and inserts intermediate images to improve motion clarity. Even fast camera pans then display correctly, but you can still see slight shadowing (double edges) in fast movements. Sony's Z series offers even more-effective motion enhancement with its 200-Hertz "Motionflow" technology - the KDL-46 Z 4500 is one example.

With movies, the LG's TruMotion system also improves motion clarity, but smoothes out the typical movie judder, an effect that won't be to every viewer's taste. It also causes picture errors such as "halo" effects, a sort of haze of pixel-noise around moving objects, since the lower frame-rate means movies provide less of the information the TV needs for generating intermediate pictures.