I recently bought a 55RU7100 and felt very unpleased with the way it displays dark scenes in 4K HDR, in which the global dimming destroys the whole image, making it impossible to watch due to low brightness and contrast. Even in a dark room, there's no strength to properly display the elements that are lit within a majorly dark scene, performing worse than my 9 years old LG LCD TV.
I noticed that both using a pendrive with HDR media and on the YouTube app the HDR is excellent for the capabilities of this model, with strong contrast far superior to anything i've seen on the other native apps: Netflix and Amazon Prime (HDR10+). The following video is displayed correctly with strong brightness on the objects among the black background: https://www.youtube.com/watch?v=9uyyOHIidMA. It seems that the global dimming does not intrude in this case.
One of the worst dark scene performances happened throughout all of the 4th season of The Expanse (HDR10+, Amazon Prime), the whole show was poorly lit and it seemed that i watched it with backlight setting close to 0. I did try using contrast enhancer to High, gamma setting to 3, different image modes and tweaking their settings, turning off eco solution, turning eco solution on with minimum backlight 50 etc. to no avail. Very bad experience overall.
I've read on other topics on this forum and in other sites a vast amount of people complaining about the global dimming across many models of Samsung TV's. Yet, no solution, not even an acknowledgement of this situation, is being done by Samsung. It's not acceptable that to have a proper image i also have buy another remote control with numbers to access the service menu and tweak things that should be done by Samsung itself, or at least have a normal menu setting to adjust or disable the global dimming. There's no point in having a deep black simulating OLED if you can't watch the scene, this is ridiculous.
What will Samsung do about this?
I guess that Samsung can disable this through a software update. I own 2 Samsung TV and they both have this issue with dark scenes.
This is the only reason that makes me admonish about Samsung TVs at the social groups I'm in.