LG C8 OLED Image Quality Analysis Review
By Chris Heinonen on
The 2018 LG C8 introduced two major new features for image quality: Direct LUT access for calibration, and black frame insertion for SDR to improve motion quality. Both of these were features that were long wanted on an OLED to offer up improved image quality but the implementation of them has to also be done right to work. So now we will look at the 2018 C8 OLED to see how well it performs purely on the basis of image quality.
LG C8 SDR Performance
For testing, we use CalMAN 2018 software along with a Klein K-10A, a Murideo Six-G, and we target the Rec.709 color gamut with BT.1886 gamma. For the LG C8, the Technicolor mode was the most accurate out of the box, which we’ve seen when doing field calibrations as well, and so we used that as our starting point. Looking at the pre-calibration data, there’s not much you need to change. The RGB balance is very close to perfect, and the gamma also tracks quite well. Color saturations are below the visible error level of 3.0, as are luminances. Even every patch on the color checker measured in below 3.0, which we get 98-99% gamut coverage. For the majority of people, I’d say to stick your display into Technicolor mode and leave it alone.
Of course, we are going to calibrate it, and in doing so we do clean up the RGB balance a bit. The average error of 1.3 before was great, but 0.2 is effectively perfect. The other error levels are similarly reduced, and the gamma tracks perfectly along the curve. We can see that the tint of green is just slightly off, but it isn’t anything you’d ever worry about, and the error levels are so low there is no reason to care.
Post-calibration, the image of the LG C8 in SDR mode is effectively perfect, and you can see why a studio might use one as a reference consumer monitor to check their masters against.
That calibration was done manually, but the LG C8 also supports using a LUT for calibration. As you can read in our piece, typically when you make adjustments to a display or calibrate it, you adjust a control which then makes adjustments to the LUT. What the C8 lets you do is bypass those controls and write to the LUT directly. This gives you far more detailed control, as where you might have access to a 20-point grayscale control, the actual grayscale LUT is 1023 points!
For the LUT calibration there is a CalMAN workflow that effectively does it all for you, so we are just looking at the end results. The gamut coverage is better now, getting very close to 100%, but look at the saturation chart for Red, Green, and Blue. We see that 100% is effectively perfect, but 90% and 80% are well off on the CIE chart. There is an issue with how CalMAN is building the LUT internally before sending it to the LG that is causing this, though they are working to resolve it and might have done so by the time you read this. Our C8 sample is gone so we can’t test it anymore.
The RGB balance is fantastic, but the gamma is off from 30% and below, potentially causing some raised shadows. We also see some color checker points that are above the visible level of 3.0, which were not there when done manually. I didn’t notice any posterization when viewing content after, but other people have when using the LUT controls to do it.
Aside from the 100% saturations bug, the LUT calibration looks to work quite well. But you can also get the same results right now manually, and unlike with a LUT you can write down those values and save them in case you need them later. Once CalMAN has the issues with the LUT fixed, then it is a faster, easier way to calibrate than the current method and should offer identical or better results. If I was calibrating today, I’d do it by hand, but in a month or two that might not be the case.
August 13, 2018 Note: Other calibrators have informed me that the late July CalMAN update resolved the over-saturation bug with the LUT, but some have said there are still a few issues being worked out with the LUT calibration still. It seems that it is getting close.
LG C8 HDR Performance
For HDR, the Technicolor preset also was the most accurate one that we tested. First, you’ll have to ignore the nits on the pre-cal info. CalMAN has been taking a low reading for the first reading of measurements. Usually, I’d just fix it by taking it again at the end, but I forgot here. Since we have a fixed nits target of 1000 and not relative, that doesn’t affect the data beyond the reading for 100%. Next time I’ll make sure to not have this happen, but it doesn’t impact what we learned.
The white balance here is very good, though it drifts starting at 70%. You can see the errors start to go much higher in the grayscale with luminance as we are targeting 1000 nits but this OLED can only do around 700-750 nits. Up until it runs out of luminance it does very well, but it can’t do anything about trying to hit 1000 nits. DCI/P3 gamut coverage is good, coming in at 95-97% and right around 70% coverage of Rec2020. Overall the pre-calibration numbers here are pretty good.
Post-calibration I didn’t make the same mistake, so you have a peak reading of 717 nits. The grayscale has been evened out so it is almost perfect, aside from not being able to do 1000 nits. The colors are mostly good, but 100% magenta moves towards blue as you can see in the Rec2020 gamut coverage chart. Color checker errors are mostly low but run into more issues once luminance is included. Gamut coverage remains the same, with very good DCI/P3 coverage after calibration.
What we see with the OLED is that it lacks the luminance to perfectly display a 1000 nits HDR signal. It is having to do tone mapping from 70% onward, which is fine. The C8 still has plenty of brightness because the blacks are perfect, so it can still look better than displays with 1000 or even 1500 nits of brightness.
We also calibrated the Cinema mode for HDR using the LUT option. We have less data here because CalMAN’s default workflow for this doesn’t capture as much, but we can still get a good idea of what is going on. Here the grayscale is even better than by hand but has the same luminance issues since that’s just an inherent issue with OLED. What we do see is a higher error reading in red, and that is because of the gamut issue we also saw in SDR with the LUT calibration. Once CalMAN has this issue fixed, the 3D LUT looks to be a bit more accurate, but doing it by hand will give you similar results in the end.
Color volume can be seen in the chart below. The C8 does well with the Dolby method compared to some cheaper LCD displays, but models that can produce more nits start to pull away from it. You won’t notice it as easily on its own, but when side-by-side with high-end LCDs the highlights on HDR are noticeably lower in saturation. As the WRGB panel in the LG has to start adding white to reach those peak output levels, it just can’t maintain the rich colors at the brightest output levels that an LCD can today, and won’t until RGB OLED is available.
|Display||MDC 1000 nits||DCI 1000 Nits||Rec.2020 1000 nits|
|Sony A1E OLED||346.40||—||—|
|LG C8 OLED||358.114||76.95%||51.59%|
LG C8 Dolby Vision Performance
Since you can calibrate Dolby Vision on the LG C8 as well, I’m going to look at the post-calibration results. We used Cinema Home as that was the most accurate most in initial measurements. Unlike HDR10, I’m using relative results here, since Dolby Vision should be doing a relative display of the content, unlike HDR10. Here the grayscale is effectively perfect, as the tracking for luminance matches the EOTF perfectly. The color checker has lower error levels as well, though still some issues with color luminance compared to grayscale. It is very accurate, as you’d expect, and only takes around 30-45 minutes to do correctly.
LG C8 Video Features Performance
Beyond having accurate colors, the LG C8 also offers superb video processing features to enhance the performance. One new addition this year is black frame insertion. We only recommend this for SDR, as the light output falls in half, but that can still get you a picture that is plenty bright for most lighting conditions. I used this extensively watching the World Cup and motion looked much better with it enabled. Some people might see a small bit of flicker, depending on how sensitive they are, but to me, it is completely usable until the BFI on some other TVs this year.
The LG C8 also has dynamic tone mapping. You can enable or disable this in the settings and it works like Dolby Vision does. If a scene is very bright, it will bring that brightness down to use the full range of the TV without as much highlight clipping. This does result in a slightly dimmer HDR image, but it depends on the scene. Flipping it on and off it would make little to no difference in some scenes and a huge difference in others. I found myself leaving it enabled because of the improved highlight details that it provides.
Motion on the LG C8 is much improved from the E6 I reviewed just two years ago. With that display, it felt sometimes like the image was stuttering, just because the motion was so instant and clear compared to an LCD or plasma. LG has worked to improve the appearance, and here you get clean motion but without extra smoothing or other issues. Using black frame insertion makes it even better, but the motion is improved compared to OLEDs from just two years ago and is much better than an LCD.
Off-axis viewing of the LG C8 was superb. In a living room that has a wide viewing area, everyone is able to watch the display with very little shift in colors or black levels compared to an LCD. However, it didn’t fare well with the skylight overhead. It would reflect on the screen and wash-out the image there quite easily. With the blinds down during the day, the LG was plenty bright to watch content with the black frame insertion enabled. With the blinds up, the sun could be more powerful than I wanted and the screen reflects a lot of that glare. If I couldn’t fix my lighting, I’d look at the Samsung Q8 or Q9 instead because of their superior anti-reflective coatings.
I didn’t notice any low-level banding with my LG C8 sample, but I also didn’t put up a 5% slide to look for it. If I don’t see it in content, it isn’t something I’m going to worry about personally and I’ve seen fewer reports about it this year compared to last year. I know the DACs used to drive the panel have changed, and that should lead to improvements in this area.
LG C8 Image Performance Conclusions
Overall the LG C8 offers remarkable performance, especially given how accurate it is out of the box. You can improve it with a manual calibration, and if they fix the issues with LUT calibrations that might be an even better option down the road. Individual memories for SDR and HDR make it easy to have both setup correctly without compromising, and the video processing has improved a lot in the past couple of years.
The main issues with the C8 are the standard OLED issues, that you can’t get as bright as an LCD and you don’t have the color saturation in those highlights that an LCD does. In most cases, if they aren’t side-by-side, you won’t notice the difference, but it just means OLED still has room to improve, especially if they can move from WRGB to RGB panels down the line.
For people that don’t have issues with reflections from uncovered windows, the LG C8 is a fantastic TV choice. SDR and HDR content looks fantastic, and the pure blacks are just so much better than an LCD can muster. For most people, it’s probably the best image in a TV this year that you can get.