I noticed something interesting when displaying near-black window patterns. If I load up a 1% window and have Smart LED set to low, the top and bottom of the screen are very black, while I can see a brighter section running across the middle of the screen where the 1% window is. Switching to the standard or high settings does not show this brighter strip across the screen, but the weird thing is, the 1% window actually shows up brighter.
I can watch this happen when I pause the pattern and the icon in the lower left from my PS4 causes the lower portion of the screen to become brighter. The icon goes away, then the screen dims. After that, there is a difference depending on the Smart LED setting. On low, the screen dims, and I barely see the window. On standard and high, the screen dims, I see the window, but then the window actually brightens slightly. It's as if the 1% level is actually getting boosted just a bit. It's definitely brighter than when I use the low setting. Anyway, not sure if this matters much, but just thought I'd post my observation.