It's possible to notice banding with 8bpc if you look at a color gradient, especially if it wasn't dithered. But if you add proper dithering (over all 3 channel

It's possible to notice banding with 8bpc if you look at a color gradient, especially if it wasn't dithered. But if you add proper dithering (over all 3 channels) and you're looking at a natural image (yeah, not a 256-color web-optimized one)... I don't know. Dithering plus higher resolution has pretty much the same effect as a higher bit depth.