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42LF65 Calibration & Picture Quality

by Vincent Teoh
30 June 2007

Calibration

There are 6 picture modes available on LG 42LF65: [Intelligent Eye], [Dynamic], [Standard], [Mild], [User1] and [User2]. But for the last 2, the rest are fixed preset – you cannot change any of the parameters except brightness via the [Bright] button on the remote control. I'm not sure who came up with the name, but [Intelligent Eye] simply refers to the picture mode where brightness is adjusted automatically according to ambient light level.

Baseline CCT (Correlated Colour Temperature)

Among the fixed presets, [Mild] came closest to D65, but was still slightly blue with delta error (dE) above 4 across the board:

Pre-calibration CCT Pre-calibration RGB Tracking
[Mild] picture mode CCT
[Mild] RGB Tracking

Calibrated CCT

Naturally I had to adopt one of the user modes (I chose [User2], but either would have been fine) to calibrate the LG 42LF65. Thumbs up to LG for allowing the settings to be saved per input independently, meaning that we can achieve the best possible picture for each source.

In [User2] mode, the [Warm] colour temperature preset was still too high, so I delved further into the [User] Colour Temperature submenu to calibrate the greyscale. I came very close to D65 with dE below 4 from 20% stimulus onwards:

CCT RGB Tracking
Calibrated CCT
Calibrated RGB Tracking

Calibrated Colour Chromaticity

The default [Colour] setting of 30 in [User2] picture mode resulted in an undersatured image, so I had to bump it up, using the CIE chart, saturation histogram and 709 colour bars as my reference. With [XD Colour] disabled, colour decoding was spot-on, and the chromaticities did not wander too far off HD 709 reference:

Calibrated CIE
Calibrated CIE with reference to REC 709

Benchmark Test Results

Stuck pixels 8
Screen Uniformity Backlight bleed in 3 corners; vertical banding
Overscanning on Component 2.5 percent (0% when 1:1 Pixel over HDMI)
Blacker than black Passed
Black level Below average
Black level retention Stable
Colour chromaticities Above average
Scaling Average
Video mode deinterlacing Very good (minimal jaggies on waving flag test)
Film mode deinterlacing 3:2 & 2:2 cadence passed when [Cinema] is on
Viewing angle Above average (120°)
Motion blur Worse than most other LCDs I've seen
Digital noise reduction Below average
Sharpness Defeatable edge enhancement
1080p/24 capability (PS3) Accepts 24fps, but judders
1:1 pixel mapping Yes, [1:1 Pixel] over HDMI

Stuck Pixels

My LG 42LF65 review unit did not suffer from dead pixels. Instead, the problem was one of stuck pixels, which are pixels that remain lit-up when they're supposed to be switched off (hence most noticeable on a black background). I counted no less than 8 stuck pixels on my 42LF65 sample, of which 5 were situated in the centre of the screen. Granted, once I moved back to normal sitting distance I couldn't really see them, but they stood out like a sore thumb when I was calibrating the television close-up. If I were planning to keep this screen, I wouldn't have hesitated one second in requesting an exchange, resorting to the Distance Selling Regulation if necessary.

Screen Uniformity

To be fair to LG, few LCD TVs have screens that are flawlessly uniform, but if I did purchase the LG 42LF65 that I reviewed, I'd be pretty unhappy. There was significant backlight bleed on 3 corners of the panel... only the bottom right was spared. Furthermore, on a mid-grey background I could see faint stripes of uneven discolouration running down the centre of the screen, which was worse on off-axis viewing. This was certainly not helped by the 42LF65's below average black level.

Black Level & Contrast Ratio

While the LG 42LF65 passed blacker than black (BTB) data without a hitch, and exhibited no black level fluctuation, its black level – both in absolute terms and after calibration – was downright disappointing, without doubt among the worst I've seen on all the high definition televisions I've tested so far.

Without backlight control at my disposal, I engaged [Black Level] "Low" (over HDMI) and dialled down [Brightness] to achieve the lowest possible black level while preserving video black. Even then, the resultant contrast ratio was an appallling 244:1, so I had no choice but to boost peak brightness (by increasing [Contrast]) slightly beyond the target level recommended by SMPTE, in order to expand the dynamic image range on the 42LF65.

As [XD Contrast] only served to obliterate shadow detail (and highlights) without materially improving absolute black level, I left it off.

Video Processing

Given the aforementioned mediocrities, the LG 42LF65's performance in video deinterlacing caught me by surprise. It was actually on par with the Sony KDL32D3000: few jaggies were seen on the rotating wheel, bouncing bars and waving flag test patterns. But then again I should have expected this... after some digging around I found out that the LG 42LF65 is actually powered by Faroudja's critically acclaimed DCDi technology.

Film mode deinterlacing was equally impressive. The LG 42LF65 detected both 3:2 and 2:2 cadence and applied the appropriate reverse pulldown fairly quickly when [Cinema] mode is enabled. But there's one catch...

Somehow I could only switch on [Cinema] mode over aerial feed (analogue/ digital TV) and component in 480i. Over HDMI (regardless of resolution) and component in 1080i, [Cinema] mode was simply greyed out and not utilisable. I tried enabling [Cinema] mode over digital TV and then swapping to HDMI to see if the settings would be carried over: the greyed-out option actually stated [Cinema] "On", but in reality 3:2 and 2:2 cadence were not detected and proper film deinterlacing was not applied.

While deficiency in deinterlacing film material is difficult to notice when the resolution is high (1080i), the easy solution to this problem is to outsource the deinterlacing process to your player device, i.e. send a progressive signal from your DVD player to the LG 42LF65.

The LG 42LF65 listed among the noisier (in terms of picture) HDTVs I've tested. Engaging various levels of noise reduction in the XD engine improved matters somewhat, but was insufficient in my opinion to elevate the 42LF65 beyond second-rate in this respect.

1080p/24 Capability

The LG 42LF65 successfully accepted 1080p/24 signal from our newly-acquired Sony PS3 (thanks again to everyone who donated), but presumably because the screen refresh rate is not a multiple of 24Hz, judder was unfortunately present.

Picture Quality

Freeview Digital TV

The first time I switched on the LG 42LF65 and started channel surfing after auto-tuning, I was horrified by the amount of pixelation, noise and motion smearing present on screen. After calibration things were much better, but the 42LF65 could still be unforgiving towards poor-quality source. For Freeview digital TV to be watchable, the programmes need to be of a fairly high bit-rate, and a viewing distance of at least 10-12 feet is advised.

Serving at Wimbledon Grass court

Rain and Wimbledon, that's summer in Britain for you. The latter provided the ideal platform for me to assess motion handling on the LG 42LF65.

Bad news I'm afraid. At moderate to high speed, the trajectory of the tennis ball resembled a comet trail. Furthermore, panning camera shots of the crowd resulted in a disconcerting degradation in image detail: individual faces and figures were undiscriminatingly mashed up into a haze of blurriness.

Wanting to rule out poor source as the cause of these motion deficits, I tuned in to watch the Wimbledon broadcast on BBC HD... only to be greeted by the same inadequacy. If anything, the higher resolution made the ghosting clearer – now I could see a ghost image closely tailing the moving tennis ball.

HD DVD

By now you should have got the hint that the black level on the LG 42LF65 is not very good at all. Even with the help of maximum tolerable ambient/ bias lighting, LG 42LF65's blacks looked murky grey most of the time, reminding me of the earliest generations of LCDs.

And a poor black-level pollutes the overall image in other ways. As this backlight is casted upon all colours and intensities demanded of the television, the entire picture – especially dark greys and colours – becomes washed out. To illustrate, when a display with greyish blacks is asked to produce dark red, a dash of grey would be added to the mix, causing the final colour to be lighter (e.g. dark pink) than it should be.

Jack Black Cameron Diaz

A perfect case in point is The Holiday on HD DVD, a romantic comedy about two charming career women with recent relationship failures who swapped homes across the Atlantic for two weeks, and ended up falling in love with local men. Predictably clichéd to the core, and overly long considering its genre, The Holiday presented little examination of the black-level performance on the LG 42LF65. Most of the scenes were well-lit, except for the part where Iris (Kate Winslet) accidentally discovered to her delight how to lower the electric blackout blind in Amanda's (Cameron Diaz) bedroom, and blackness (ok, greyness) descended on the screen.

But what the movie did offer was quite a lot of close-up facial shots which were necessary for character interaction and development. This is where the LG 42LF65 was let down by its below average black level. In spite of respectable colour chromaticities and accurate colour decoding, flesh tone looked depleted and unconvincing. Deeper blacks would probably have conferred more vibrancy and depth to the detailed but ultimately flat image portrayed by the LG 42LF65.

PS3 Console Gaming

Gran Turismo HD

I had a quick go at Gran Turismo HD Concept on Sony PS3, and was immediately wowed by the scarily realistic high-definition clarity rendered by LF4265's [1:1 Pixel]. Still, motion blurring remained evident as my Mitsubishi Lancer whizzed past the cheering (or booing) crowd... and my drifting still sucks.


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