I think it must be me then, since I didn't catch it at all with my old Kuro, or for the first 300 hours or so of the ZT.
But here's the thing -
It's not that the black bars seem deeper when the screen is bright - it's that the black bars get lighter when the screen gets brighter - AH. Wait.
Now I'm confused. Then that would be ABL.
Settings are at 80 Contrast, 10 Brightness, on Professional 1.
I think it may just be my eyes, since I've searched all the forums on the internet and no one else seems to have experienced this.