LG 42LM660T 3D Smart TV Review

2D Calibration

Note: Our LG 42LM660T review sample was calibrated using Calman Professional, the industry-leading video calibration software.

We used the “ISF Expert1″ mode as a starting point. First of all, we approached the LM660T from the perspective of a user who will not be spending any extra money having the TV calibrated. We had to select the “Just Scan” aspect ratio from the Q.MENU to disable overscan with 1080i/1080p content, shut off the motion interpolation [TruMotion] feature, and also shut off the [Edge Enhancer]. All in all, we were left with a good image from only making these adjustments.

Greyscale

Pre-calibration RGB Tracking
Pre-calibration RGB tracking and delta errors (dEs)

Similarly to the last LG LCD-based HDTV we looked at, the 42LM660T measured as being just a touch too red in its out-of-the-box performance. However, the slight tint was by no means severe, and isn’t likely to change the intended impact of the video material being viewed. For an out-of-the-box preset, this is very, very good going.

Post-calibration RGB Tracking in [ISF Expert1] mode
Post-calibration RGB tracking and dEs in [ISF Expert1] mode

We typically find that LED LCD TVs have very linear greyscale tracking, except in the darker areas, which tend to be tinged blue. This was the case with the LG LM660T – we used our Klein K-10 colorimeter and CalMan software to measure the colour of grey at 10 different brightness levels, and then offset the controls in the 2-point Greyscale menu accordingly, to neutralise the red tint. We were still left with some excess blue at the 10% and 20% positions, so we switched into the 20-point mode (which tops up, rather than replaces the adjustments made in 2-point mode) to neutralise these areas, too. The result is visually perfect greyscale tracking. Bravo, LG.

Gamma

It wasn’t possible to fully linearise gamma tracking on the 42LM660T, although the resulting inaccuracies are small. The menu features a [Gamma] option, from which 1.9, 2.2 and 2.4 can be chosen. The lower number (1.9) would be suitable for a very bright room, with 2.2 being the suggested setting for rooms with a little bit of light, and 2.4 for darker rooms. We selected 2.4 for night viewing, and calibrated for this.

Gamma curve in [ISF Expert1] mode Gamma tracking in [ISF Expert1] mode
Gamma curve in [ISF Expert1] mode Corresponding gamma tracking

The dip downwards at the 10% stimulus position on the chart to your top-right indicates that shadow areas are slightly exaggerated. In reality, this is likely to be caused by the IPS panel’s inability to block enough light from the LEDs from reaching the viewer’s (or in this case, our calibration meter’s) eyes. As a result, darker areas appear slightly illuminated. Interestingly, near-white shades were actually a little too dark, although this isn’t too visible with content.

When we reviewed the LG 42LM620T, we discovered that it had some dimming present at all times during dark scenes. Interestingly, the 42LM660T has this option fully selectable. The above charts were captured with the LM660T’s [LED Local Dimming] feature turned off. Don’t confuse this “Local Dimming” for the rare and usually very expensive LCDs which locally dim many areas behind the screen; the “Local Dimming” on the LG 42LM660T is limited to a smaller number of zones. However, enabling this feature will cause the television’s LED light sources to dim during darker scenes, which does help mitigate the slight greyness of the IPS panel’s blacks. It’s not for free, though: this will also dim any bright details that coexist with the darkness in these scenes (a moon in a pitch-black sky being the best example). Enabling this feature will of course shape the gamma tracking curve in different ways, depending on the type of test pattern used (full screens will give different results to windowed patterns).

Colour

The LG 42LM660 manages to saturate nearly all of the HDTV Rec.709 gamut, but like many LED-based LCD televisions we’ve seen, it can’t quite hit the fully saturated green or red extremes (the former being more noticeable than the latter). None of these are particularly visible issues, since from our experience, a slight under-saturation is much less damaging to the realism of the picture than the more extreme over-saturation we used to get in the days of CCFL-backlit LCD (there’s no radioactive green grass on this TV).

Pre-calibration CIE chart in [ISF Expert1] mode
Pre-calibration CIE chart with reference to HD Rec.709

The pre-calibrated measurements above also reveal the slight exaggeration of red in the greyscale: all of the colours, including the white point in the middle (which should ideally show an absense of colour) are gravitating towards red.

Post-calibration CIE chart in [ISF Expert1] mode
Post-calibration CIE chart with reference to HD Rec.709

After calibrating greyscale and using the 42LM660T’s [Colour Management] menu, we could rectify small inaccuracies which remained in the image. As you can see, we couldn’t get all of the outer extremes of the gamut to saturate fully, since the combination of the panel and the light sources simply aren’t capable of producing a completely deep red shade. This is still excellent performance, however, and is enough to produce very natural images.

Post-calibration Luminance levels in [ISF Expert1] mode
Post-calibration colour luminance (coloured bars = targets; black bars = measured values)
Colour saturation tracking
Post-calibration colour saturation tracking

Saturation tracking was very good, with no serious deviations from linear colour being observed. Again, the extreme outer edges show the inaccuracies caused by the panel’s slight colour gamut limitation, but colours are on-target below the full saturation point, with a gentle slope into the less saturated extreme.

We compared some animated content with a reasonably wide range of colours (Arrietty) on the LG 42LM660T as well as with a Panasonic plasma featuring supremely accurate colour, and most of the time, had a very difficult time picking one from the other in terms of colour reproduction (putting the many other differences between LCD and plasma images aside). The biggest difference was in the LG’s inability to produce a completely accurate blue: deep blues in night time scenes appeared more purpley.

3D Calibration

The many positive aspects of the passive 3D display system were revealed when it came to measuring, and calibrating, the LM660′s performance in the third dimension. Because the panel itself operates much the same as it does in 2D – only allocating every second line on the screen differently – there are no greyscale, gamma, or colour performance limitations imposed by the higher refresh rate required by active 3DTV sets.

3D Mode Greyscale

3D Pre-calibration RGB Tracking
3D Pre-calibration RGB tracking and delta errors (dEs)

Unusually, pre-calibrated Greyscale tracking was better in the 3D mode than in 2D! We can only assume that this is down to luck, and that the slight blue tint added by the particular pair of polarized 3D glasses we attached to the front of our measuring device counteracted the TV’s own red tint by more or less the correct amount. The effect diminished the brighter the image got, though, as you can see at the top-right of the chart.

3D Post-calibration RGB Tracking in [ISF Expert1] mode
3D Post-calibration RGB tracking and dEs in [ISF Expert1] mode

The 20-point Greyscale control is available in 3-D mode, however, it didn’t always seem to work properly: we adjusted the controls and saw the changes, but they disappeared as soon as we left the menu. This is why we still have a small excess of blue lingering at 10% stimulus and a slight touch of red at 100%. However, the performance here is still excellent, with all but the blue tint in dark areas being indistinguishable to the eye.

3D Mode Colour

The full colour management menu is available in tri-dimensional mode, resulting in excellent performance.

3D Post-calibration CIE chart in [ISF Expert1] mode
3D Post-calibration CIE chart with reference to HD Rec.709
3D Post-calibration Luminance levels in [ISF Expert1] mode
3D Post-calibration colour luminance (coloured bars = targets; black bars = measured values)

Benchmark Test Results

Dead pixels None
Screen uniformity Good for an LED LCD: slight darkening around edges
Overscanning on HDMI 0% with “Just Scan” aspect ratio, but physical screen border obscures roughly half a pixel on all sides
Blacker than black Passed
Calibrated black level (black screen) 0.155 cd/m2 (Local Dimming Off)
Calibrated black level (ANSI checkerboard) 0.155 cd/m2
Black level retention Stable with [LED Local Dimming] off
Primary chromaticity Very good
Scaling Excellent
Video mode deinterlacing Very effective jaggies reduction
Film mode deinterlacing Passed 2-2 PAL and 3-2 NTSC tests
Viewing angle Very Good for an LCD TV; colours remain largely saturated but blacks brighten
Motion resolution 300 lines
Digital noise reduction Optional
Sharpness Defeatable edge enhancement
Luma/Chroma bandwidth (2D Blu-ray) Full Luma, Chroma horizontally blurred
1080p/24 capability No judder in 2D or 3D; [Real Cinema] mode must be enabled
Input lag 31ms compared to lag-free CRT
Full 4:4:4 reproduction (PC) Yes, with “PC” input label

Power Consumption

Default [Standard] mode (2D) 54 watts
Default [Standard] mode (3D) 60 watts
Calibrated [ISF Expert1] mode (2D) 45 watts
Calibrated [ISF Expert1] mode (3D) 73 watts
Standby 1 watt

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