I don't understand your point: the orientation of the lighting is irrelevant with respect to suppressing melanin production. The cold temperature of the Kindle LEDs, ostensibly selected to make the screen appear white in the presence of warmer ambient lighting, is likely to have enough of a blue component to disrupt sleep. Total luminescence isn't a factor in suppressing melanin production either, as someone else has posted in this thread, so automatic dimming doesn't help either. The automatic dimming, if it worked well (it didn't in my case) would help reduce eye strain by matching the Kindle screen brightness with the ambient light level.