I have zero banding, and just a very small amount of DSE. Is everyone's screens flush with the bezel? Mine has a very tiny gap where the screen isn't flush with the bezel just above the Sony label. I included some pics from watching some of 4k HDR The Martian Extended version last night with all the lights off.
These were taken with my Galaxy S7 edge. Some in regular mode, and others in HRD mode. The HDR mode of the camera does a good job at picking up extra light your eyes don't see due to a slightly longer exposure. This also adds to the lens flare effect that happens as well. Keep in mind, a lot of what the camera sees is not what your eyes will see.
The First pic is showing an extreme angle pointed down at the bezel and screen, you can see some lights... but I don't think it is affecting the screen pq in any way.
The second pic is the Samsung logo from the screen saver on the 4k bluray player. it's soo bright and taking pics with my camera phone, it pretty much just looks like a flashlight shining on the screen.
The main menu is hard to get a good pic of as well, since the background is grey and not black, so that has everything to do with exposure with the cell phone camera. I used the HDR mode of my cell's camera in order to get some of the 'Brighter' pics that actually show the bezel of the screen. Otherwise, when you are sitting in front of this thing, it just looks amazing.
The credits is really hard to capture. The black bars look like there is no light. There can be a little shown on extreme angles, but I never plan on watching tv at that extreme of an angle.
I figured I would throw some pics from a rather bright scene in there as well. For those that haven't seen the movie, it's a really funny scene. Again, this is really hard to capture. I had the backlight at either 40 or 45. I don't see much of a difference with the backlight setting from 40 through Max (50) on HDR content. Until someone can take an actual measurement of the light output of this display to see if there is, we won't really know. Most other content I have the backlight set to either 10 or 15, sometimes 20, but at night, even 20 is waaaayy tooo brigtht. 10 to 15 seems perfect with most content.
Let me know what you think, and also for those of you that have this tv, please look at the screen around where it meets the bezel to see if there are any gaps. I have no banding on this screen, and very little DSE, so I doubt it would be worth exchanging, but I figured I would at least ask you if you're shows any lights at all. you will need a scene that either takes up the entire screen, or a really bright scene in a movie for those bezel lights to be on obviously, so use your best judgment.