Dr. Raymond M. Soneira, DisplayMate:
One behavior of the iPhone 4 Auto-Brightness that is a serious operational error or bug is that it locks onto the brightest ambient light sensor value that it has measured at any point starting from the time it was turned on, and then continues to use that highest value indefinitely to set the screen brightness until the display turns off â€“ either by cycling through sleep mode or full power off. This means that the screen brightness is frequently set too high, which wastes power and can cause eye strain if you move to lower ambient light levels.
I am not too fond of my gadgets automatically altering the brightness levels of the display. I think our visual systems do a much better job of adjusting to different ambient light conditions. One major problem with displays that auto-adjust brightness is that it messes with our expectations of how bright the display should be based on our last experience. For instance, if the brightness level was at 60% when we last looked at our iPhones the next time we turn it on that’s what we expect. And if the iPhone auto-adjusts the brightness to say 30%, when we were expecting 60%, the experience is uncomfortable.
According to Dr. Soneira it isn’t just the iPhone: Android as well as TVs have similar auto-brightness bugs that make them ineffective. Make sure to hop on over to DisplayMate for possible solutions.