Samsung 2020 QLED Local Dimming Problem

Summary and Petition for Resolution

I own a Samsung Q90T TV. This TV (and other 2020 QLED models) has a serious problem with the "local dimming" setting, which is critical for viewing HDR content, which should be a core capability for a TV such as this one. See description below.

Online Petition

If you own a Q90T or any other similar TV with this same problem, please sign the petition. This will help show Samsung how widespread the problem is. Please include your TV model number in your entry. Also please contact Samsung, report the problem, and reference the petition URL. There are multiple ways to contact. Use them all; the more they hear of this problem, the better!

Description

To reproduce the problem, follow these steps:
  1. Reset TV to factory settings.
  2. Enable HDR for HDMI4 (this is "input mode plus" in the settings).
  3. Disable ambient light detection.
  4. Disable anynet+.
  5. Set local dimming to "standard".
  6. Connect an HDR source to HDMI4.
  7. Power the TV off then on, and start a timer.
  8. At exactly 6 minutes, you'll see the screen get much darker. This is equivalent to local dimming being reset from "standard" to "low" (even though it's actually still set at standard). In other words, the TV stopped respecting your chosen setting for local dimming.
  9. If you open the settings and change local dimming to "low" and then back to "standard", the setting will start working again, but again it will only work for exactly 6 minutes. So, if you want to watch a 2 hour movie and keep local dimming on "standard" the whole time, you'll need to open the settings menu every 6 minutes... no less than 20 times in those 2 hours!
  10. As a sidenote, there is a related bug where even with non-HDR content, the screen will randomly dim suddenly. E.g. when watching a 2-hour movie, there will be a small handful of moments where brightness drops dramatically in the middle of the scene (this is harder to reproduce, since it does not happen reliably at 6 minutes like the one described above).

Documentation

The problem is widespread. It has been described in numerous forum discussions, including one on Samsung's own forum with 2000+ comments:

History - A Successful Resolution

For those of you who are worried Samsung will not respond to this plea, there is indeed hope. In 2007, a similar community petition convinced Samsung to fix a video problem on a different TV (see here).