Yeah, I had like a bright white sun against a black background and noticed when I unlocked it kind of exploded from the inside out, again, just the nature of OLED, very cool.
Inspired by the second wallpaper from the first page, I decided to go out to Fulton center in NYC this afternoon to take this photo and edited it to B&W. It works pretty well so sharing that here. One cropped out like how I have on my phone but one full frame so you guys can move around as you wish.
My guess: Some of the darker shades of grey must cross a threshold of brightness within the software before activating the OLED pixels. Therefore as the wallpaper fades in the different shades cross that threshold at different points