LG 55LM6700 HDTV Review- When 120 Hz Isn’t 120 Hz-Updated

July 3rd, 2012 · 34 Comments · 3D HDTV, Connected TVs, LED LCD Flat Panels

Note (7/7/12): We’ve added an update below to reflect changes due to a new firmware version.

 

All LED LCD TVs have an inherent problem with motion resolution. For this reason, HDTV makers adopted higher refresh rates, namely 120Hz and 240Hz. These faster rates reduce motion blur, but at a price premium over “standard” 60Hz models. LG claims the 55LM6700 has 120 Hz refresh. After extensive testing, we find this claim very misleading. The 6700 failed to show any improvement in motion resolution compared to any 60 Hz HDTVs we’ve tested.

So what’s the story?

First, the Features

The LG 55LM6700 is the 2012 version of its highly rated 2011 LW5600 series television. New for 2012 is an attractive thin-bezel style LG calls “Cinema Screen.” The 6700 is the entry-level for this top LED LCD series. Major features include Smart TV with streaming movies and apps, passive 3D, a Magic Motion remote and LGs so-called 120Hz refresh.

120 Hz?

Until the arrival of the LM6700, all 2012 120 Hz refresh HDTVs employ  a circuit called Motion Estimation/Motion Compensation (ME/MC). These chips analyze consecutive original frames then create and insert synthesized frames between the original frames. This results in better motion resolution. To date, using the industry accepted FPD reference disc, we’ve found every 60 Hz LCD we’ve tested has about 320 lines of resolution. With ME/MC circuit engaged on a ME/MC circuit-equipped 120 Hz HDTV, the motion resolution increases to 600 lines.

All 60 Hz HDTVs use a technique called 3-2 pulldown, which converts the 24 original frames to 60 Hz by displaying the same frame three times then the next frame twice,  then the next one three times etc. During pans, this uneven cadence creates a jerkiness called judder. We use a judder test sequence on the Marvell Qdeo test disc to test whether TVs created smooth motion with 24 frame sources.

LG’s Version of 120 Hz

We asked LG if any of its 2012 HDTVs with a factory specification of 120Hz refresh rate employ an ME/MC chip. The response was no. LGs spokesperson told us they are using a technique called “Black Frame Insertion.” Their claim: in between the 60 active images, LG shuts off the LEDs sequentially from top to bottom. This shortens the time the LCD panel is illuminated in section by section thereby reducing motion blur.

60 Hz LCDs sample a frame and keep the same image about 16.67 ms. This allows little time for the pixels to move to create the next frame. The panel holds the image and then repositions the pixels quickly for the next frame. Our eyes and brains are programmed for seeing continuous motion, not sample and hold, change and repeat. The result is we see smear know as motion blur.

A proven  technique to reduce motion blur is to sequentially darken the image from top to bottom, making that portion of the frame black instead of an illuminated still image. This reduces the visible hold time and the brain perceives sharper motion. This is the technique LG claimed to use in the 6700.

Our Test Results

To confirm LG’s  backlight scanning claim we used a video camera recording at 480 Hz (four times the 120 Hz claimed refresh rate). We then chose a slow-motion playback of 15fps to illustrate the LED shut off sequence. As you can clearly see in the video, the 55LM6700 does not employ top to bottom scanning. Instead, it shuts off the LEDs at the sides, then the center and repeats the sequence.

 

Contrary to LG’s claim, this technique had no effect at all on the TVs motion resolution. We tried Cinema and Expert picture modes and observed the same results, 320 lines of motion resolution, the same motion resolution as every make and model 60 Hz LED and LCD we’ve tested to date. Furthermore, there was always judder present, again confirming 3:2 pulldown as in a 60 Hz display. We were able to shut off the blinking LEDs by placing the TV in its “Game” mode, and found the motion blur results were the same as when the lights were blinking, only 320 lines of motion resolution .

We presented our findings to LG. They confirmed the LEDs in the 55LM6700 are only mounted at the bottom of the screen, making a vertical scan impossible as they would have to be mounted under on the left and right edges). LG provided its own 24fps judder test material; however, we saw the same judder as observed using our Qdeo test disc.

Based on our findings we asked how they could call this HDTV a 120 Hz model. Their response: “With respect to these advanced testing methods, the results illustrated are an overly magnified representation of the average user experience; what really matters is what consumers can see with their own two eyes.”

LG continues to post on its website, and dealer descriptions, simulated photos showing a significant reduction of motion blur with its claimed “TruMotion 120Hz” refresh. (photo below)

We find these claims incorrect and unsupportable based on the FPD motion resolution tests used by HD Guru and other major well-respected TV reviewers. Our high-speed camera clearly shows LGs scanning claim to be incorrect as well. This TV is a 60 Hz LED LCD. All tests yield no motion blur reduction compared to any 60Hz TV.

Overall Performance

We measured the 55LM6700’s red, green, and blue color points, minimal black level, image uniformity, signals processing and color temperature.

Using the LGs “Rec. 709″ picture setting, primary colors measured reasonably close to the industry standard actual (Rec. 709 reference in parenthesis):

Red x 0.635, y 0.343 (x 0.64, y 0.33);Green x 0.311, y 0.606 (x 0.30, y 0.60); Blue x 0.153, y 0.061 (x 0.15, y 0.06).

Signal processing was excellent, passing the HQV standard and high definition tests for jaggies, detail, 3:2 pulldown and deinterlacing of 1080i.

Black level uniformity was not good. Light areas (often called “flash lighting”) along the top edge and top corners were distracting in dark scenes. However, white level uniformity was good.

A backlight setting of 44 in the “Expert” picture mode produced a white level of 29.91 ft. Lamberts, a level bright enough for most homes with any type of ambient daytime light control (such as window curtains). The black (minimum luminescence) level at this setting was “fair” at 0.010 ftL. The LM6700 has a “local dimming” control. We did not observe deeper blacks and using normal source material we noticed less contrast ratio, not greater as one would expect. Given this display only has a single bottom row of LEDs we surmise this control is really a type of dynamic gamma, since true local dimming would require direct back lighting or LEDs on the vertical and horizontal edges.

The brightest image available is 76.31 ft.L reached in Vivid mode with the default setting of 100% contrast and backlight. This setting produced light blacks and is far brighter than any normal room would ever need.

The passive 3D in the 6700 uses inexpensive glasses (supplied) and produces and image of 1920 x 540 per eye rather than 1920 by 1080 as seen in active designs. The performance was typical: a visible line structure and some jaggies on edges are noticeable on diagonal objects or with white lettering against a black background. 3D does provide excellent depth with good source material.

Grayscale at the Warm factory default measured slightly too warm 6232K at 20 ft lamberts and 6113K at 80 ft lamberts.

The screen surface is smooth, highly reflective and not very effective in limiting reflections from lamps and other light sources.

Smart TV

LG includes Netflix and Vudu (not tested) as well as some of its own 3D shorts. We sampled four 3D travel videos and found very low 3D production values, not a way to impress your friends. This LG adds and Internet browser and apps.

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Remote

The Magic Motion remote is like a Wii controller requiring tilting to move a cursor over the desired buttons. We find it slow and cumbersome. An LG spokesman says a conventional remote is available as an extra cost option.

 

Conclusion

The LG  55LM6700  offers svelte, contemporary styling with many features. We are disappointed by LG giving this TV 120 Hz specification as its motion resolution and judder is the same as every 60 Hz TV we’ve ever tested. However, compared to competitors’ offerings with LED edgelighting, thin form factor, 3D, Smart TV with browser, it’s priced quite aggressively, currently under $1450 ($2300 MSRP). HD Guru awards the 55LW6700 ♥♥½ out of five hearts rating.

Update

When we made our review measurements, we used the latest firmware available at the time (version 3.20.31). LG pushed new firmware after we wrote the review. The latest firmware (version 3.21.40) added a TruMotion control for frame interpolation. We retested motion resolution and judder. We also evaluated the TruMotion control settings with  a variety of film based (native 24 frame per second) movie content as well as video sourced HD content.

The new TruMotion menu has four main choices: User, Smooth, Clear and Off.  There is a second setting for Judder control which available in the “User” mode and grayed out all other modes. Using the Qdeo test disc, we checked out all possible settings.

In “Clear” and “Smooth” mode film judder is eliminated. The “User” mode required the “Judder” control to a setting of 7 or higher take effect. We did not observe any difference in the image (other that the elimination of judder) in either the “Smooth”, “Clear” or User at “7″ or higher. Because of the 4th of July holiday, we were not able to reach our LG contacts to explain performance differences of the three modes and if so tell us what content would be required to see it.

Like other HDTV we’ve tested in the past, the judder observed during panning 24Hz sources is eliminated by a motion estimation/compensation which creates new interpolated frames that are inserted in between the actual film frames. When activated the TruMotion settings also gives film based sources video-like look often referred to as the “soap opera effect”.  For more on the soap opera effect artifact, read our article here.

When testing video based content such as 1080i and 720p native content (i.e. sports, news, and other unscripted programs) the TruMotion settings have no effect.

Next we retested motion resolution in all TruMotion modes. The 55LM6700 performed the same as with the prior firmware, with 320 lines of motion resolution, just like every other 60 Hz TVs tested. This confirms the 55LM6700 remains a 60 Hz refresh HDTV.

We applaud LG for upgrading the series by offering the option of anti-judder.  However, we still do not consider a panel refreshing the image 60 times per second and simply flickering LEDs (which has no observed effect on motion resolution contrary to LG’s product claim) to qualify for a  factory stated 120Hz refresh specification. Our ♥♥½  (2.5 out of five) heart rating is unchanged.

Disclosure:  The 55LM6700 used in this review is a LG supplied loaned sample.

 

 

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34 Comments so far ↓

  • Cindy Lou Who...

    *I meant to ask if you could include a list of those TV’s from the 2013 and new/upcoming 2014 line that also have this deceptive marketing false frame rate claims.

    With LG our general rule of thumb is 120Hz Trumotion is just assumed to be 60Hz by those who know, and a 240Hz Trumotion set is assumed to be 120Hz with some actual Trumotion & (Anti-Judder/Anti-Blur settings) like in years gone by; in say the 32LD550 as an example with TRUE Trumotion 120Hz interpolation capabilities.

    Great News! An LG spokesperson told HD Guru in January that its upcoming 2014 HDTVs will be abandoning the “Tru Motion” spec in favor of the panel’s native refresh rate. If you look at Amazon you will see the 2014 LG HDTVs, which are all “LB” series product now list the native refresh rate along with a CMI (Clear Motion Index) number which is LG’s proprietary test method for motion resolution. To date LG has not provided any information as to how this CMI number is arrived at. If an when they do, we plan to report it to our readers.

    In the meantime you can now get the “true” panel refresh to make accurate comparisons between different models and competitors that also provide accurate information. Unfortunately some brands continue to list an XXX Hz effective refresh, in lieu of the panel’s native refresh rate.

    We commend LG for seeing the light and now providing the panel’s native refresh rate in its specs.

    HD Guru

  • Cindy Lou Who...

    Still running into Sales people @ Stores like Sears that know “nothing” about this.

    When confronted with sites like yours, well that was last years (now two years ago)…

    COULD YOU PRETTY PLEASE Update this to include what those from the 2013 & 2014 lines?!?

    So many sites (Slickdeals have people informed thanks to your work about at least the LG & a few other models) but it’s amazing when someone doesn’t speak up on that thread or AVS forum how and entire group basically gets duped by these lying practices. Some day there maybe a class action lawsuit and those affected will end up receiving $15 +/- and that will be the end of it.
    There should be a truth in advertising push like exists with Monitors/TV’s requiring that actual image or diagonal dimensions be listed.

  • moganesh

    Hi. I sometimes find that there are images not formed correctly when view in HD. Like there is lines of vertical boxes of the the frame. How to solve this issue please. Thanks

    I do not know what you are describing. To determine if it is a TV problem or a source box problem, try a different HDMI input with a different source such as Blu-ray player. If you do not see the issue it is probably your source box (i.e cable or satellite) and not the TV

    HD Guru

  • assefa

    good

  • DavidW

    You see to have danced around this issue without addressing it: does real cinema with trumotion off produce 5:5 pull down or does it produce 3:2 pull down with black frame insertion?

  • ScanX

    Hello HD Guru, did you tested 55LM7600 or any other LM7600 already? Could you plese post a link? I would like to see the differences between 55LM6700(6600) and 55LM7600. Thanks a lot.

  • Eric

    Sounded like it did do something for the judder. Would also like the option to have the SOE effect.

  • Eric S

    If you’d read the article, the software update did not help, nor would it for the 4600. There is no hardware to create the other 60 frames per second, so they display a blank/black screen….they are displaying 120 frames per second, but we are/were assuming all 120 frames have content in them.
    Most people do not like TVs which create fake frames anyhow.

  • Eric

    Wish you guys could get LG to give the 55lm4600 users a Tru-Motion setting like they advertise! Guess we are left in the dust…Not cool LG! You need to give this software update to all your TVs you advertise with Tru-Motion. Not just the one that got the attention from this site.

  • Rick

    Hello,

    I got the same question as George on the 13th of january. LG has the new update firmware 4.31.30, are there any improvements with this firmware?

    Hope to see a update soon :)

  • silentsunami

    Any chance you will be reviewing budget LED TV LS5700 from LG?

  • Perhaps?

    Hello,
    is there a list somewhere of TVs that have stated 120Hz and yet are not truly 120Hz?
    For example how many other LG models are doing this?
    And other brands? And how can we tell at the store?

    We wrote about it here
    http://hdguru.com/beware-of-phony-lcd-hdtv-refresh-rates/7726/

    Unfortunately, the problem may be spreading. We wish there was a way for consumers to determine if the refresh rate is really the stated one, but one needs commercial test discs and high speed cameras to learn what is really going on.

    Go to the set makers website and look under specs for the native rate, if it does not appear call its customer service dept. and ask about the native refresh rate. If you see manufacturer specific terms next to the rate such as SPS, Motionflow rate, or CMR it is NOT the true refresh rate. One more item. To date no company has made a LED LCD with a native rate higher than 240 Hz. 480 Hz and above is not the refresh but native + scanning backlight at best. We wish ever TV would maker was required to list the true refresh but they are not.

    HD Guru

  • Awa

    HDGURU,

    i have tried LG tech support and needless to say, not very helpful at all. I have trouble accessing the punctuations on the keyboard when trying to log in on smart apps. it’s weird because when i want to browse the internet, the entire keyboard is fully functional. it is only when i’m trying to log in to smart apps? has anyone run into the same problem?

  • George G.

    Hd guru,
    Did you repeat test on the lg lm6700 with their latest firmware of 4.31.30. Does it now refresh or show 600 lines as opposed to the 320 lines you state for 60hz tvs. Please help

  • none

    Between a forced timing 120Hz panel and a relaxed 60Hz panel I will ALWAYS choose the 60Hz panel. It will not overshoot and it will display color as pure as possible.
    Since passive 3D does not require aggressive timings and most people simply HATES trumotion, would you agree that the 120Hz is simply a mistake of marketing from LG rather than a real world performance drawback?

  • H.H.

    Glad i stumbled upon this review, as i was days from buying this set. So may i ask is this the same issue with the lm6200? If not i guess i will shell out the extra couple of hundred and get the lm7600, which i inntitially wanted but was trying to save.

  • Eric the voice of reason

    Display Mate (online) performed an excellent test and review of LG’s passive 3D. Each eye sees half the resolution, but don’t forget that together, the two eyes see the whole 1920×1080… They have a lot of thoughful comments, and clearly are highly respected; etc.
    Active 3D had a lot of crosstalk I guess due to the glasses not switching back and forth quickly enough. The passive 3D clearly was better in their testing and they explain why.

  • Levi

    Hi. Could you please explain the apparent contradiction in your article?

    quote 1:
    “We asked LG if any of its 2012 HDTVs with a factory specification of 120Hz refresh rate employ an ME/MC chip. The response was no.”

    quote 2 (from your Updated test):
    “Like other HDTV we’ve tested in the past, the judder observed during panning 24Hz sources is eliminated by a motion estimation/compensation…”

    So, does the unit have an ME/MC chip or not?

    The 6700 uses software to create frames between the native frames of 24 Hz based content. Our tests revealed the motion performance remains the same as all other 60 Hz refresh LCDs (with either CCFL or LED lighting) we’ve tested.

    HD Guru

  • Jack

    Thanks for the explanation!

  • Jack

    Sorry for being a noob, but I thought that 120hz is a requirement for a 3D tv? Can a 60hz display logically be able to dish out 3d video?

    Passive 3D that is used by LG on all of its LED LCDs . It does not require 120 Hz for 3D. The method is a film pattern retarder bonded to the screen that employs line by line alternate polarization, which provides the 3D effect. Only active 3D which uses shutter glasses requires at least double the 60 Hz frame rate.

    HD Guru

  • Ruman

    Did you already do it? What is the result?

  • Brian

    I bought a 55lm6700 and thought it was great at first. Then I noticed on some of my Bluray Movies it was GRAINY. I have a Audioquest (coffee) HDMI cable so I don’t think its a cable problem. As far as it being blurry, on fast motion scenes it is for sure. I see dark lines for a split second. I am pissed off and will would love to file a class action if they wont own up to there mistake. I bought this tv a few months ago and spent a lot more on it then it costs now. I never had this problem when I had my SONY XBR.

  • None

    “We disagree. A number of vendors still provide the refresh rate as the refresh rate. Samsung provides refresh and its own “CMR” rating.

    We see this a bad trend, as we have written about how a number of TV makers are only putting there own rating on the box and not the actual refresh rate on the box. The major difference with this TV is LG states it as Hertz (Hz) while other vendors call it something else. For example Vizio states SPS for scenes per second, not as Hz refresh.

    Our big complaint: if you are going to call a TV 120 Hz it should perform like a 120 Hz TV. We’ve retested the LG with the latest (this week) firmware update. The 6700, now has a toogle for TruMotion 120. With Trumotion engaged the TV still produces only 320 lines of motion resolution we’ve found in all 60 hz refresh TVs, not the 600 lines motion resolution we’ve seen in every 120Hz refresh TV tested. The new TruMotion function does stop film “judder” smoothing pans, but at the same time it also produces the “Soap Opera Effect” making film look like video. We will update review today or tomorrow to reflect our tests of the updated firmware.”
    HD Guru

    Simply not true (the part about LG being the only one). In most countries Samsung uses the Hz moniker for their CMR rates, too. Philips does the same thing. Try to look up their new “800 Hz” and “1200 Hz” TVs. Sony is on the good path, yes, but most others are not.

    Have you even followed the TV market for the last few years?

    We’ve commented on other set makers here

    We are a USA based website. We only have access to US models to test and verify performance claims.

    If you are looking information or tests on European or Asia TVs you’ll need to find another website that’s based there.

    HD Guru

  • Kh

    LG definitely misled me as i can not believe my new LG TV is acting like picture frame at times while old tube is smoothly showing the same video.

    True 120hz must have helped if i truly had it.

    We Truly need True120hz not Falst TrueMotion.

    Time for ClassAction if LG is is not willing to exchange.

  • sharath

    I agree with the results. The guy who reviewed on CNET concluded that the motion performance is similar to 60Hz TV. I bought this tv on Best buy and returned in after a week. You can clearly see the motion related issues when you sit close to the Tv, around 5-6 feet.

  • San

    I bought Lg 55LM6200. When i play Xbox Forza 4 game and hit the scroll button . It display 1o80p at 60 hz. Why it display 60 Hz if the panel is 120 Hz. Please help on this.

  • Danny

    How is it that LG can use the term Hrz. And not be accused of false advertisements? I can see how a maker can see if they were to use their own “term”. But isn’t the Term of “Hrz” a set guideline that has a rule of measurement, a proven agreed upon rule, where as if they were to call it LGvision then LG could set its own guidelines?
    I think there was some shady dealing going on and it needs to be brought to light “publicly”

  • Robert

    “As far as a TV requiring 120Hz to do frame interpolation (ME/MC), you are incorrect as evidenced by the upgrade of this 60 Hz TV” What incredibly circular and bogus logic. 24 doesn’t divide evenly into 60, that’s what leads to the judder (3:2 pulldown). BTW, if the panel is 60hz, how can it insert black frames every other frame? It is updating 120 times a second with every other frame being black, ergo it is a 120hz panel. Do your 480 fps test again shooting 24fps content and 3D content and count the frames. It’s 120hz panel. And if you call this 60hz, then you have to call most Samsung “480hz” tvs 120hz (at most) because they do black frame insertion as well.

  • Robert

    You neglect to mention the firmware version and your settings. My set displays 24fps content with no pulldown with the correct motion menu settings. That’s impossible if it isn’t 120hz. Odd that you neglect to mention your motion settings in all those “technical” paragraphs, but mention useless values like the backlight setting which will be variable for most users. I smell an agenda.

    We’ve updated the review to reflect the new software changes (see above). As far as a TV requiring 120Hz to do frame interpolation (ME/MC), you are incorrect as evidenced by the upgrade of this 60 Hz TV, (however, this is the first LCD 60 hz flat panel we recall using ME/MC).

    Yes, we have an agenda. It is to test, and verify manufacturers’ product claims and to benchmark a given TV performance in areas that affect the viewing experience. We’ve debunked false claims in the past (such as back when 1080p panels did not properly deinterlace 1080i and only displayed 540 lines of resolution not the 1080 as claimed) and will continue to do so.

    We recently purchased a high-speed digital camera (used in the video above) and plan to incorporate it in future reviews, when appropriate.

    HD Guru

  • None

    How can you be so surprised by your findings? :)

    This is an industry-”accepted” way of stating Hz now, and the same was true last year and for some the year before that. Backlight scanning is now included in the numbers and some manufacturers even include other refresh systems in the Hz number, too.

    This is absolutely not exclusive for LG. LG was actually one of the last TV manufacturers to incorporate the new diluted measurement method. Samsung was one of the first.

    We disagree. A number of vendors still provide the refresh rate as the refresh rate. Samsung provides refresh and its own “CMR” rating.

    We see this a bad trend, as we have written about how a number of TV makers are only putting there own rating on the box and not the actual refresh rate on the box. The major difference with this TV is LG states it as Hertz (Hz) while other vendors call it something else. For example Vizio states SPS for scenes per second, not as Hz refresh.

    Our big complaint: if you are going to call a TV 120 Hz it should perform like a 120 Hz TV. We’ve retested the LG with the latest (this week) firmware update. The 6700, now has a toogle for TruMotion 120. With Trumotion engaged the TV still produces only 320 lines of motion resolution we’ve found in all 60 hz refresh TVs, not the 600 lines motion resolution we’ve seen in every 120Hz refresh TV tested. The new TruMotion function does stop film “judder” smoothing pans, but at the same time it also produces the “Soap Opera Effect” making film look like video. We will update review today or tomorrow to reflect our tests of the updated firmware.

    HD Guru

  • George

    The new update version is 03.21.40

  • Nick

    There is also a firmware upgrade for last year’s 5600 series, which also allows user control of TruMotion settings. Check it out!

  • Simon

    Any chance you will be reviewing the 55LM7600? Would like to know if the claimed 240Hz is legit or just marketing jargon.

    Yes. We already requested a sample from LG and expect in the not too distant future.

    HD Guru

  • George

    There is a new software update which adds the 120Hz option. Get the update and run your test again.

    We checked our software for the latest version (as we always do) before running all our tests late last week. We will check for a new version soon and if there are any new results we will report them in an update.

    HD Guru

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