Image: LG

Astounding picture quality aside, LG’s 2019 and 2020 OLED TVs provide plenty of gamer-friendly HDMI 2.1 features such as ALLM (Auto Low Latency Mode) and VRR (Variable Refresh Rate). Unfortunately, HDTVTest’s Vincent Teoh has reported that the latter is marred by a significant caveat: gamma/brightness shift.

What this basically means is that when VRR is enabled on LG’s HDMI 2.1 OLED TVs, the picture diverges from the calibrated values, resulting in an incorrect increase in black levels. As the OLED Association explains in its letter (which confirms the issue), this is a notable problem that could result in a loss of shadow detail in scenes.

Forbes’ reported LGE’s 2019 and 2020 OLED TVs variable refresh rate (VRR) implementation sometimes causes the image to undergo a brightness/gamma shift that makes dark areas in games look greyer and more washed out than they do with VRR turned off. By toggling the AMD FreeSync feature in the LG OLED TVs menus on and off with the Gears 5 HDR calibration screen playing with the VRR feature on, the black floor is raised and, as a result, there’s less visible shading detail in the dark areas of the left side of the Gears 5 calibration image, which is noticeable when the TV’s instant game response feature is turned off and switched to a picture preset other than the Game. There are also reports of noticeable instability/flickering in some dark gaming image areas when using VRR on LGs 2019 OLEDs.

Gamma for OLED is optimized and fixed for 120Hz by establishing a fixed charging time for OLED sub-pixels. VRR is used when the frame rate is less than 120 Hz. When the OLED TV uses framerates less than 120Hz, the gamma curve is inconsistent with the frame rate. For example, a 40Hz frame rate is longer than 120Hz frame rate. Therefore, the lower frame rates results in sub pixels that are overcharged, causing flickering of dark gray images, which is noticeable for dark images rather than bright ones, because human eyes are more sensitive to low gray colors. LGD will likely solve this problem establishing multiple gamma curves optimized for lower frame rates.

Unfortunately for LG 2019 and 2020 OLED owners, Teoh noted that the VRR gamma shift issue is inherent to the panel, which means that it can’t be fixed via software means and will require newer hardware.

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15 Comments

  1. I wonder if it could be partially mitigated by tweaking the input signal with a special color/brightness profile. It would likely not be able to be 100% fixed, but it may improve the image.
  2. I’d say suffer is a bit of an overstatement. I don’t have the equipment they have for testing but hands down the image quality I’ve seen with my C9 is the best I’ve ever seen on any display so far. If it wasn’t for this story I’d been none the wiser to anything being wrong because it really is amazing. I’ve tested 1440p/120 Hz and 4K/120 Hz, both with HDR10 and G-Sync and never noticed anything. In fact, PC-HDR on this is more of a definitive experience compared to what I’ve seen with other displays.
  3. 48” CX (2021 version probably, so CXI?) + GPU to drive it are probably my next computer purchases.

    I have a C7, but it lacks 120Hz and VRR. I’m tempted to drag my computer into the living room and hook it up anyway

  4. 48” CX (2021 version probably, so CXI?) + GPU to drive it are probably my next computer purchases.

    I have a C7, but it lacks 120Hz and VRR. I’m tempted to drag my computer into the living room and hook it up anyway

    I’m curious. What makes you lean in this direction instead of one of the made for PC ASUS and other Free/G sync monitors?

  5. I’m curious. What makes you lean in this direction instead of one of the made for PC ASUS and other Free/G sync monitors?

    Well, a couple of things

    It checks almost every box in a monitor I’ve been looking for for gaming: OLED, HDR, 4K, VRR, 120Hz. The only strike against it is that I was looking for a a 27-32”, 48” is a bit big for my setup. But I imagine I can make it work with a wall mount, it just isn’t optimal for my desk setup.

    Other than that, cost. Similar monitors are running as much or more, but check fewer boxes.

  6. Well, a couple of things

    It checks almost every box in a monitor I’ve been looking for for gaming: OLED, HDR, 4K, VRR, 120Hz. The only strike against it is that I was looking for a a 27-32”, 48” is a bit big for my setup. But I imagine I can make it work with a wall mount, it just isn’t optimal for my desk setup.

    Other than that, cost. Similar monitors are running as much or more, but check fewer boxes.

    Honestly, I have been very impressed with LG’s OLED’s I’ve seen in stores. They look great.

    I’m not really clear on what the differences between their models are though. There are so many of them, and they all look the same to me.

    I guess it’s moot though, only two are offered in 48", the CX and C9. No idea what sets them apart. Scrolling through the specs pages I don’t see much in the way of difference.

    Also, how are they doing 4k 120hz with only HDMI? Are they dropping Chroma mode substantially? Or is there some sort of compression going on there? Are there any special GPU requirements?

    It’s a tough choice to me. Gaming monitor with perfect size (43") or one of these that is IMHO too large with too low pixel density for desktop use.

  7. C9 is simply the 2019 model and CX is the 2020 model. There is no 48" C9; they started at 55".

    The spec hasn’t changed much. In some ways the CO is actually better, in that it can decide DTS audio and has a better HDMI chip. The CX supports FreeSync but this doesn’t really add much.

    HDMI 2.1 supports 4k 120Hz. You need a GPU that supports HDMI 2.1, such as the Nvidia GTX 30×0 series.

  8. I’m not really clear on what the differences between their models are though. There are so many of them, and they all look the same to me.

    To be fair to you, they are almost identical, at least to look at.

    The Letter denotes the model, the number (or roman numeral) denotes the release year.

    All models in the same year have the same OLED panel. Starting with the 2019 year, I believe, the C series and up get a better processor, which can do scaling and some things like that a bit better than the B series – the difference in image isn’t huge since it’s the same panel, but it’s something that can be measured. The high end (G/W/Z/etc) series have some premium features, such as glass screen rather than plastic, floating mounts, better built-in sound, etc. But the picture would be identical to the C series.

    B and C series are what normally go on deep discount around this time of year.

    The same panels are also what get sent out to other manufacturers (Sony, Philips, etc.) – but they all provide their own processors and software for them.

  9. My only question is that since this article covers the C9 & CX models. There is also the 2020 GX model. (pretty much the same specs as a CX just bezel-less) does the GX models also have the same VRR issue within its panel? Feel free to leave a reply.
  10. I wonder if the new Vizio HM1 OLED will suffer this same issue since LG makes their panels?

    This is more of a chipset thing.

    While in general I’d expect someone other than LG to do worse, Vizio does have a record of over-delivering at least when it comes to their UI and compatibility, so I’d rate it as 50 / 50.

    Honestly if Vizio can succeed where LG and Sony so far have failed, they’ll likely find themselves a captive market to supply :)

  11. My only question is that since this article covers the C9 & CX models. There is also the 2020 GX model. (pretty much the same specs as a CX just bezel-less) does the GX models also have the same VRR issue within its panel? Feel free to leave a reply.

    The GX uses the same image processor as the CX, so I imagine it has similar issues.

  12. This article is making me feel better about being too poor to afford one.

    Not to make light of anyone’s economic situation, but you can get a really good OLED TV for less than the cost of a really good GPU any more… and they are actually on the shelves. Yeah, you can get cheaper TVs for sure, but the OLED price tag isn’t nearly as steep as it used to be, especially if your willing to wait a bit. The TV cycle always tries to have new models announced at C3, available for Superbowl at some high MSRP, but then prices always drop significantly in the fall, and those late year and year old models go at steep discounts. LG and others often go to nearly half of MSRP.

    The difference between years is often slight – although 2018-2019 did step it up to HDMI 2.1 with 120Hz input, and 2019-2020 added Freesync. Just have to look out a bit, usually you aren’t missing out on much if you get a model from the previous year.

    Computer monitors, on the other hand… entirely different story.

    I have a C7, it wasn’t exactly an impulse buy, but I did get it on a deep discount (was a massdrop deal at the time I think) and I wanted to replace a aging Samsung TV – just happened to be right price at the right time. The first time I started a HDR PS4 game, my jaw dropped. It was pretty impactful seeing something that I always had just discounted as showroom floor gimmicks actually playing out live in my living room – with pretty much anything I threw at it to watch. Especially HDR content.

    Now I can’t look at IPS without sighing a little. It makes me weep at my computer monitors. It made the VA TV in my bedroom look like utter washed out trash, and it was a decent set at the time I bought it. The only thing that even comes close are the old Plasma screens.

    Yeah, burn in… I’ll take the risk. It looks that good that I’d probably buy another even if it did happen.

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