This isn't a lighting problem it's a metering problem, the phone doesn't know what to expose for when you're pointing it at something without eyes so you get inconsistent results.Using my iPhone still working on proper lighting for it. Not much to see for grain. Sandblast finish with dark brown stain.
The iPhone knows how, if you tell it: touch the screen at the point where you want focus/exposure to be taken; a yellow square will appear and you'll see the lighting change.This isn't a lighting problem it's a metering problem, the phone doesn't know what to expose for when you're pointing it at something without eyes so you get inconsistent results.