Review: LG 55C8 4K/UHD HDR OLED TV

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This year’s crop of LG OLED TVs represents the company’s seventh generation of large-size flat panels based on OLED technology. That’s pretty remarkable when you consider that large-screen OLED TVs were nothing more than pie-in-the-sky future-tech demos at CES only a decade ago. Granted, they still tend to be more expensive than comparable LCD TVs—if you can even call OLED and LCD comparable! Each technology has its pros and cons. For example, OLED has better blacks, uniformity, and off-axis performance, while LCD is generally brighter and less expensive for similar screen sizes.

LG’s entry-level model line is the B8, and next up the ladder is the C8, followed by the E8 and W8, all of which use the same OLED panel. (Last year’s G7 will remain in the lineup for a while, so a G8 isn’t imminent.) I wanted to review the C8 because it’s the least-expensive line that includes the new Alpha 9 video processor, so LG sent me a 55″ C8, which lists for $2799.99 ($2499.99 promotional price). Moving up to the 65″ version costs exactly $1000 more than the 55″ model, while the 77-incher goes for a cool $8999.99.

Features

As we learned at CES last January, LG’s 2018 OLED TVs (except the B8) have a new, more powerful video processor, dubbed the Alpha 9. It exhibits a 35% improvement in CPU and GPU power and a 50% increase in DDR memory capacity. (The B8 has the equivalent of last year’s video processor.) The Alpha 9 supports a four-step noise reduction and decontouring algorithm (doubling the two-step algorithm in last year’s processor), an object-based depth enhancer, and an adaptive color enhancer. In addition, the internal color lookup table (LUT) has been increased from 17x17x17 (4913 points) to 33x33x33 (35,937 points), which results in much greater color accuracy.

The Alpha 9 also supports high frame rates up to 120 fps with 4K/UHD resolution via USB and 2K/HD resolution via HDMI 2.0. (HDMI 2.1 could be implemented in the 2019 models, but that isn’t certain.) Of course, there is currently no consumer content at 120 fps, but video games are pushing that envelope.

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The new Alpha 9 video processor is a real powerhouse.

Regarding high dynamic range, the LG OLED TVs are the only ones on the market to support four flavors: HDR10, Dolby Vision, HLG, and Technicolor. Even better, these TVs apply dynamic tone mapping to HDR10, which includes static metadata, and HLG, which uses no metadata at all. These features are called HDR10 Pro and HLG Pro, respectively. Dolby Vision and Technicolor already use dynamic metadata. In addition, a feature called HDR Effect expands SDR content to simulate high dynamic range. Finally, the 2018 OLED models include black-frame insertion, which the 2017 models did not provide.

Another important development is LG’s partnership with Technicolor. Along with support for Technicolor’s HDR system, which is officially known by the unwieldy name “Advanced HDR by Technicolor,” the LG OLED TVs include a preset picture mode called Technicolor Expert. This mode aims to replicate the performance of a mastering monitor as closely as possible—which includes shifting the white point away from the conventional D65 standard!

Why do that? When the measured coordinates of the white point are equal on different types of displays (such as LCDs, xenon projectors, and OLEDs), they don’t look the same to human eyes. In order to match the perceived appearance of images on these displays, the white point must be offset. For example, in Technicolor Expert mode, the white-point CIE coordinates are 0.300, 0.327 rather than 0.313, 0.327. This is said to remove a magenta cast in WCG (wide color gamut) content if the white point is at the conventional location on the CIE diagram.

Thanks to a partnership with Portrait Displays, all 2018 LG OLED TVs can now be calibrated automatically using the industry-standard CalMan calibration software by SpectraCal, which is part of Portrait Displays. This feature allows CalMan to directly access the TV’s internal 3D LUTs, which results in very precise adjustments to the color performance without needing an outboard—and expensive—LUT box. Even better, CalMan’s AutoCal function can calibrate standard dynamic range (SDR), HDR10, Dolby Vision, and HLG, assuming you have a pattern generator that can provide suitable test patterns.

It’s important to note that the LG implementation of AutoCal is performed at the hardware level, not the user-interface level, which avoids any potential for interference between the menu settings and CalMan’s tweaks. This is a major improvement in the calibration process that greatly reduces the time required to perform a full calibration for each picture mode.

Yet another important feature is support for Dolby Atmos immersive sound. Of course, the TV’s speakers can’t fully re-create an immersive soundfield—even the large soundbar included with the W8. The important point here is that a Dolby Atmos bitstream can be sent via HDMI ARC (Audio Return Channel) to an AV receiver or Atmos soundbar. The bitstream is encoded in Dolby Digital Plus, not Dolby TrueHD. Also, the AVR or soundbar must be able to inform the TV via HDMI CEC (Consumer Electronics Control) that it is Dolby Atmos-compatible.

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The connections include four HDMI inputs, three USB ports, antenna/cable RF input, legacy AV input, optical digital-audio output, and Ethernet port.

The LG OLED TVs offer the company’s new AI ThinQ user interface, which is built on top of the webOS smart-TV platform. This enables voice control using more natural commands, such as “It’s too loud” and “Turn off the TV when this program is over.” You can also ask other questions, such as “Do I need an umbrella today?” No wake-up word is needed, since the system listens only when you push a button on the remote. The TVs are also compatible with Google Home and Amazon Echo products, which do require a wake-up word.

Other tweaks in the 2018 models include the addition of an “apply to all inputs” option as well as a menu control to turn dynamic tone mapping on and off directly. This is welcome news for all calibrators. Also, the Game-mode HDR tone curve is now similar to the Cinema-mode tone curve.

Ergonomics

All 2018 LG OLED TVs provide the same menus, LG’s WebOS 4.0 smart-TV platform with AI ThinQ, and the Magic Remote, which you wave around to move the cursor on the screen. Among the important features here are hot buttons for Netflix and Amazon on the remote and the ability to define other hot buttons on the numeric keypad.

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The Magic Remote includes hot buttons for Netflix and Amazon, and you can define the numeric keys to be hot buttons for other apps.

You can also display your own photos and videos from a mobile device and even watch 360° VR content by waving the Magic Remote to change the perspective. A Magic Link icon identifies similar content to what you’re watching and calls up additional info, such as the cast of a show or the lyrics of a song.

The menu system and WebOS user interface are straightforward; I had no problem finding my way around them. Even better, the functionality of the Magic Remote has been significantly improved. The previous generation felt clumsy and inaccurate as I waved it around. I found it difficult to position the cursor where I wanted it without overshooting. This year, the response is a bit slower, making it easier to put the cursor where I wanted it to be.

Calibration

Calibrator extraordinaire David Abrams of Avical measured the LG 55C8 before and after he performed a full calibration for SDR, HDR10, and Dolby Vision content. He used SpectraCal’s CalMan software and the Colorimetry Research CR-100 colorimeter profiled with a CR-250 spectroradiometer. The test-pattern generator was the SpectraCal VideoForge Pro. All calibrations were performed using the new AutoCal feature implemented for LG’s 2018 OLED and Super UHD LCD TVs.

I’ve included the results of David’s calibrations at the end of this review. If you’re technically inclined, take a look. Meanwhile, I’d like to discuss some issues with AutoCal that have come up in this thread.

Several calibrators have discovered a bug in CalMan’s AutoCal function. The 3D LUT it generates for SDR results in exaggerated colors at 100% saturation—107% to be precise. Lower saturation values are not exaggerated. SpectraCal is aware of the bug and working to fix it. The company expects a beta version of the software with the fix to be available in late June. However, I don’t think this is a terrible problem, since real-world content rarely includes colors at 100% saturation.

Strangely, some people report that some colors are generally undersaturated, especially red. I don’t know why this would be true in SDR if colors with less than 100% saturation measure as accurate. I can see how it might be true in HDR, since the white subpixel is boosted in HDR to increase the brightness, which also desaturates the color. According to Neil Robinson, Senior Director of Strategic Partnerships at LG with deep technical knowledge about the 2018 TVs, the white subpixel is not boosted much below a luminance of about 400 nits, so only high-brightness HDR is desaturated by it. The white subpixel is not boosted at all in SDR, so there should be no undersaturation in that content caused by the white subpixel.

Some participants in the thread claim that LG’s OLED TVs do not use 3D LUTS for HDR. But according to Neil, they do use 33x33x33 LUTs for HDR as well. In this case, however, CalMan generates the LUT by measuring only red, green, blue, and white at 100% brightness and calculating the entire 3D LUT from those measurements. CalMan calls this a “Matrix LUT” because it’s effectively a 3×3 matrix implemented in a 3D LUT. The oversaturation problem at 100% saturation is still evident in this case, which will be fixed in the update.

Another reported problem is banding and other artifacts, especially in low-light gray areas of the image. According to Neil, this can occur because 3D LUT algorithms attempt to correct the grayscale after it has already been calibrated in the step preceding the color calibration.

For example, let’s say that one point in the calibrated grayscale has a delta-E error of 0.5, which is well below the threshold of human perception—it’s essentially perfect. But the 3D color-LUT algorithm still sees it as an error and tries to correct it. However, the resolution of the 3D LUT is too low—even with nearly 36,000 points!—and the “correction” can actually make the error worse, which can lead to banding and other artifacts. Remember that, in 8-bit SDR, there are over 16 million colors, while in 10-bit HDR, there are over 1 billion colors, so there’s a lot of interpolation involved in both cases.

The best solution is to create a 3D LUT algorithm that ignores the white points or “neutral axis” of the 3D LUT, which forms a diagonal line through the 3D LUT cube from one corner to the opposite corner. Apparently, this update is on the CalMan-development roadmap, but there is no announced release date for it.

Other problems identified in the thread include the need for manual adjustments after doing a grayscale calibration, which uses a 1024-point, 12-bit 1D LUT. After running AutoCal on the grayscale, David Abrams found that he didn’t need to make further manual adjustments for SDR, but he did need to do some tweaking for HDR because the set came out of black too slowly. He raised the Brightness control one click and adjusted some of the low-level DDC (Direct Display Control) points manually in CalMan.

BTW, CalMan offers a maximum of 61 points in its 1D grayscale LUT; the other points are interpolated. According to David, it takes only a few minutes to complete this task.

Some have reported a 20% drop in peak light output after completing the 1D and 3D LUT calibration. According to Neil, this is due to the fact that CalMan starts with the panel’s native response rather than the factory-calibrated response. He goes on to say there is always a significant drop in luminance when you change the white point from the panel’s native point to D65.

The thread also includes reports of CalMan commonly crashing if too many LUT points are used. One calibrator recommends using no more than 3000 points, and he typically uses only about 1000 points, which he claims yields better results than using more points. Still, even 1000 points doesn’t avoid the issues discussed in the thread.

David runs CalMan—which is a Windows program—on a Mac. He says it does tend to crash more when he runs it within Virtual Machine, but not within Boot Camp. He reports that the number of LUT points does not affect the frequency of crashes he experiences.

Regarding the number of points in the 3D LUT AutoCal process, the maximum number in CalMan is 10,000, though you can elect to calibrate fewer than that. (The rest of the 36,000 points in the 33x33x33 LUT are interpolated.) He says that using more points generally yields better results—with diminishing improvements above 5000—but it also takes a lot longer. For example, using a Colorimetry Research CR-100 or Klein K10 colorimeter, it takes about four hours to complete a 3D LUT run with 10,000 points. Still, to get the best result possible, he calibrated the 55C8 in this review with 10,000 points.

There are two obscure bugs in LG’s firmware that I should point out. One appears with Dolby Vision content at 1080p, which is the resolution of Dolby Vision patterns from the VideoForge Pro and Murideo Six-G pattern generators. If different patterns are sent without sufficient time between them, the screen flickers. But since there is no commercial Dolby Vision content at 1080p, and it’s not a problem with 4K/UHD content, few would even notice it. For those who do, updated firmware with the fix is now available for downloading on LG’s website.

The other bug appears intermittently when loading a 3D LUT. Sometimes, it seems to load, but it is not applied to the image. According to Neil, the workaround is simple: Switch to a different HDMI input and back to the input you’re working on. This forces the TV to load the LUT. LG is working to fix this bug, but no timetable has been announced. In any event, I don’t see it as a serious problem.

Test Discs

Given all the complaints about banding in low-luminance gray areas of an SDR image, I started my testing with the FPD Benchmark Blu-ray. In particular, that test disc—which was never commercially available—includes two gray ramps, one from 0 to 100% brightness and the other from 0 to 25% brightness. There was some banding in the 0-100% ramp, especially in the low end of the ramp, and lots of banding in the 0-25% ramp. I have yet to see a TV that doesn’t have lots of banding in the 0-25% ramp, so no surprise there. The 0-100% ramp had a bit more banding than some other TVs I’ve seen, but it was not tremendously worse.

The color tests on that disc all looked fine—they did not appear to be undersaturated. These test images include WRGBYCM patches at various brightness and saturation levels and a Gretag-Macbeth color chart. In addition, the color chart showed virtually no color shifts when viewed far off axis.

Looking at the HQV Benchmark 2.0 Blu-ray, the video- and film-resolution tests were all excellent. In addition, the C8’s Random Noise control worked well to reduce random noise, even at the Low setting. However, the MPEG Noise control did little to improve compression noise other than soften the image a bit.

Turning to the Spears & Munsil HD Benchmark v.2 Blu-ray, I discovered that a couple of pixels were being cropped from the edges of the screen. It turned out that the pixel-orbiter function—which is designed to combat image retention—was enabled by default. To disable it, you must go into the OLED Panel Settings and turn Screen Shift off, which did the trick. Other observations from that disc include very good white-field uniformity and confirmation that off-axis viewing changes the color very little.

The Samsung HDR10 Reference Disc UHD Blu-ray—also not commercially available—includes one pattern with patches at 10, 1, and 0.1 nits, which were clearly distinguishable. Also, horizontal and vertical sine waves in black and white as well as magenta and green looked clear all the way to the highest frequencies, with only very slight banding in the highest horizontal frequency.

When I first looked at this test disc, David had not tweaked how the set comes out of black in HDR, and some of the low-light dynamic-range tests looked like they were coming out of black too slowly. After David adjusted this, they looked much better. And the bright shots looked fabulous! So did the natural-color tests—green leaves, brown bark, purple flowers, yellow and red fruit, and skin tones all looked entirely natural.

Also on this disc are some great motion-sharpness tests—for example, panning over a bunch of rocks. This looked very juddery until I engaged the TV’s TruMotion frame interpolation, which smoothed it out considerably. Of course, this also introduces the dreaded soap-opera effect, making 24 fps content look like video. Slow-moving fine-detail images on this and other test discs all looked excellent.

Finally, I checked out the HDR/10 Bit/WCG tests. Looking at the same shot of clouds drifting by a shoreline in 8 and 10 bits, they looked virtually identical, a real testament to the Alpha 9 processor’s de-contouring. However, in a couple of other scenes, the image seemed to brighten a bit shortly after it was first displayed. In particular, I noticed this in the shots of ducks, trees with foliage, and white frost on trees. I haven’t noticed this before, and I don’t know what caused it.

Real-World Content

In the thread about the problems with AutoCal, I asked for some suggestions for real-world content that was especially egregious in terms of banding and other artifacts. Other than replies like, “It’s obvious with all content,” the only specific recommendation I saw was the opening scene of Skyfall. James Bond is looking around a dimly lit apartment with lots of opportunities for banding. I looked at this scene very carefully, but I saw virtually no banding or other artifacts. There might have been a hint of banding in the shot as he’s descending the dark stairwell before emerging into the bright sunlight, but it was barely visible.

One of my favorite Blu-rays to use for examining shadow detail is Master & Commander. Immediately after the main title, the image fades up from black to a night shot of the ship at sea. The fade-up was a bit blocky, but nothing terrible. Shortly after that, there are a few shots below decks as the night watchman makes his rounds. The shadow detail in these shots was superb, better than I’ve seen on many TVs, and there was no sign of banding or posterization in the low-light areas. Shortly after sunrise, the ship is in a fog bank, which exhibited no banding or posterization, either.

Another of my go-to Blu-rays is Stargate: Continuum. The opening starfield was superb—very deep black with many more stars than I’ve seen on just about any LCD TV. I did see very slight banding in the dark-blue sky over the Tok’ra city in which bad guy Ba’al is about to get his comeuppance. Chapter 3 begins with a low-light shot of the steamship Achilles sailing across the Atlantic Ocean at night, followed shortly by another low-light shot in the cargo hold. The shadow detail was excellent with no visible banding, though there was some random noise in the very dark areas.

Moving on to UHD Blu-ray, I took a look at Black Panther in Dolby Vision. Again, the opening starfield was wonderful with super-deep blacks. In chapter 2, T’Challa stops a caravan in the jungle at night. Much of this scene is very low APL, and I observed excellent shadow detail with no banding. In all scenes I looked at, the colors were exquisite, detail was stunning, and highlights were very bright.

I also looked at Gladiator in Dolby Vision on UHD Blu-ray. The orange clouds behind the title exhibited some banding, especially as they dissipated, but this was short-lived. Overall, the image was a bit noisy, which was probably film grain. The flaming arrows and catapult projectiles in the first battle were quite bright with very little clipping, though the fires in the Roman camp after the battle were pretty clipped.

To check clipping a bit more, I turned to Batman v Superman and Pan, both in HDR10 on UHD Blu-ray. At 1:09:00 in Batman v Superman, Bruce Wayne’s white shirt clipped quite badly in the bright, flickering light. This was somewhat worse than I’ve seen on some other TVs. At 0:09 in Pan, the sun clips a bit, but it wasn’t bad.

Passengers on UHD Blu-ray in HDR10 looked gorgeous. The opening starfield was a deep black, and the Avalon’s deflector was very bright. Unlit passageways were super-deep black, and the colors and detail were wonderful. The bright flame of the ship’s reactor clipped a bit, but it wasn’t bad at all.

I also checked out Billy Lynn’s Long Halftime Walk in HDR10 on UHD Blu-ray. This is the only commercial title I know of with UHD/HDR content at 60 frames per second. As with all TVs, I had to enable the HDMI inputs to accept 18 Gbps; this is off by default to maximize compatibility. The control, called Ultra HD Deep Color in the LG, is in the Additional Settings menu, and turning it on allowed Billy Lynn to play at 60 fps with no problems.

I love the HDR shots in this movie, especially interior shots with a window looking out to the daylight beyond. These shots looked great on the LG C8, with both interior and exterior parts of the image properly exposed. Shadow detail was excellent in the uniforms as Bravo squadron waits outside the hotel as well as in the limo on the way to the Cowboys’ stadium. Likewise, color and detail were superb. I realize that many people don’t like the look of 60 fps, but I really do.

Conclusion

When I read through the thread identifying various problems with AutoCal and the LG C8, I was concerned. So, I paid particular attention to the issues raised in that thread during my review. After David Abrams did the AutoCal and I did extensive testing, I saw almost no indication of any issues discussed in that thread. Yes, I did see some minor banding in a few cases, but nothing egregious or even noticeable unless you’re looking for them. In the end, I just don’t think these issues are significant for the vast majority of users.

I’m sure that some will dispute my observations and conclusions. All I can say is, I call ’em as I see ’em. If I had seen horrible artifacts, I definitely would have reported them.

LG’s OLED TVs continue to get better and better, and the C8 is no exception. It’s one of the best TVs I’ve ever reviewed. It offers just about everything anyone would want in a modern 4K/UHD HDR-capable TV—except 3D, which many people still enjoy. In particular, AutoCal with CalMan is a great new feature. Granted, it’s going through some birthing pains, but I have no doubt those will be fixed in short order. Even as it is today, real-world content looked spectacular to me with no obvious problems.

The LG C8 is more expensive than many premium LCD TVs of similar size, and it’s not as bright—though it’s plenty bright enough under most conditions. Also, as the brightness of the image rises above 400 nits, the OLED’s colors become less saturated than an LCD’s as the white subpixel is boosted.

On the plus side, it has superior blacks, shadow detail, uniformity, and off-axis performance. The colors and detail are second to none, and the video processing is top-notch. It’s no wonder that so many professional color-grading suites include an LG OLED TV along with a pro monitor.

I am delighted to bestow the AVS Forum Top Choice award on the C8, and I highly recommend it to anyone shopping for a premium flat-panel TV. If you have the budget, I bet you won’t be disappointed!

Many thanks to David Abrams of Avical for measuring and calibrating the LG 55C8, and for allowing me to do my evaluation in his studio. Thanks also to Neil Robinson of LG and Tyler Pruitt of SpectraCal for their help with this review.

Review System

Sources
Oppo UDP-203 UHD Blu-ray player
SpectraCal VideoForge Pro test-pattern generator

Setup & Test Discs
HD Benchmark (Blu-ray)
Digital Video Essentials: HD Basics (Blu-ray)
FPD Benchmark (Blu-ray)
HQV Benchmark (Blu-ray & DVD)

Calibration Results

We had some unexpected problems with the pre-calibration measurements, so we need to redo them. I will add those measurements to this section soon.

Here are the post-calibration results in SDR. David calibrated the ISF Expert (Dark Room) picture mode:

SDR Grayscale and Gamma:

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SDR Colorimetry:

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Here you can clearly see that the primary and secondary colors at 100% saturation are oversaturated. Colors saturated less than 100% are pretty close to their targets.

SDR Colorchecker:

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Next, the post-calibration results for HDR10. David calibrated the Cinema (User) picture mode:

HDR10 Grayscale and EOTF:

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HDR10 Colorimetry:

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HDR10 ColorChecker:

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Here are the post-cal results for Dolby Vision. Here again, David calibrated the Cinema (User) picture mode:

Dolby Vision Grayscale and EOTF:

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Dolby Vision Saturation Sweeps:

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Dolby Vision ColorChecker:

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Finally, here’s the spectral distribution of the C8:

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