LG’s CX and C9 OLED TVs may look exquisite, but they have a serious issue with displaying content with variable refresh rate (VRR) enabled. From washed-out dark areas to image flickering and instability, VRR is currently a no-go on some of LG’s expensive OLED TV series. A firmware update may not be able to resolve the issues, either.
Microsoft and Sony may be on the verge of bringing 8K and high-refresh-rate gaming to consoles, but some high-end TVs are struggling to keep up. LG has included support for variable refresh rates (VRR) in its CX and C9 OLED TVs, for example, although there have been some problems with its implementation.
In September, LG acknowledged that some OLED TVs had ‘VRR issues’, which translates to dark colours looking grey and washed out when VRR is enabled. Additionally, there have been reports of dark areas being unstable and flickering with VRR enabled. Gamma optimisation is apparently at the root of the issue, according to the OLED Association. LG Display explained the issue as follows in a statement to the OLED Association:
Gamma for OLED is optimised and fixed for 120 Hz 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 120 Hz, the gamma curve is inconsistent with the frame rate. For example, a 40 Hz frame rate is longer than 120 Hz frame rate. Therefore, the lower frame rates results in sub pixels that are overcharged, causing flickering of dark grey images, which is noticeable for dark images rather than bright ones, because human eyes are more sensitive to low grey colours
LG states that it will attempt to resolve VRR issues by ‘establishing multiple Gamma curves’ for lower frame rates. However, HDTVTest remarks that a solution is unlikely to arrive in the form of a firmware update, as he outlines below. In short, it is unclear how, or if, LG can fix these VRR issues on existing TVs.
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Alex Alderson, 2020-11- 6 (Update: 2020-11- 6)