Before I used the stark white wallpaper for the lock screen it was clearly evident that regardless of the brightness setting, the iMessage box where you type messages was white, and everything else was gray. Now, with the new wallpaper, starting at about 40% brightness the entire background is the same bright white color as the iMessage box. Not suggesting I have recalibrated my display by using different wallpaper, but I do think there is something in the iOS concerning opacity which makes the wallpaper you are using highly relevant when viewing notes, iMessage, mail, etc. This new wallpaper fixed the problem on my Pro 11, which I can compare with my X.