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You’ve had it happen to you before: you're in a dark room with nothing but your smartphone, and as soon as you switch it on to check your email, your eyes are quickly regretting that decision. Turning on that smartphone was like taking off your sunglasses and staring directly in the sun. You might then turn down the brightness on your phone for a later time, but the device is still using a ton of power to output that light. Smartphones can use as much as fifty percent of the total phone power just to light up that LCD display, draining its precious battery.
Dr. Raymond Soneira, President of DisplayMate technologies, decided to investigate the benefits of the Automatic Brightness setting because of the reason. He found that Automatic Brightness is really just a marketing feature from manufacturers to try and boost the specifications of the handsets they're selling. But, Dr. Soneira cautions that by doing this, companies are actually doing more harm than good because the displays aren't getting the engineering attention and expertise that it needs to fix the problem. Before the Automatic Brightness control can get the attention it needs, Dr. Soneira says that it needs to gain the "respect" and appreciation of consumers, manufacturers, and even governments.
To start, it's important to understand how the automatic brightness actually works. Smartphones have a light sensor located in the bezel that measures the ambient light so that the mobile operating system can appropriately dim the screen or raise the brightness. For example, if you enter a dark room, the phone would automatically adjust itself so that it’s dim enough to comfortably read in the dark. When the ambient light level is higher, the screen also needs to be bright so that there is no glare from the light reflected off the screen and because, hey, it hurts the eyes.
Unfortunately, this sensor doesn't work as it should most of the time, and that's because the sensor is actually facing you and measuring the brightness of your forehead and face rather than the ambient level lighting, or the room you’re in. In order to fix this, companies would need to install a rear and side facing ambient light sensor with a different angular profile so that it doesn't just fixate on what is directly in front of it. But of course, this is not happening anytime soon.
Dr. Soneira adds that in addition to malfunctioning light sensors, automatically adjusting the brightness is a bit of a fluke as well. All three of the smartphones that were tested have operation bugs or errors with their automatic brightness. Users cannot adjust the display for their own preferences on a whim. Dr. Soneira stresses that automatic brightness should adapt without the user having to go through a ton of menus just to do so—it should be as easy to adjust the brightness levels of the display screen as it is for users to adjust the volume in a cinch.
Optimal screen brightness varies from person to person, and though it’s all relative it’s still important that each user is able to look into a screen that doesn’t pierce their eyes. Dr. Soneira conjured up a formula that figures out what the optimum brightness is and how smartphones displays are so terribly inaccurate. The iPhone 4, for example, doesn't have much of a sliding scale in between measures of brightness, which means that users aren't getting the preferred brightness scale in each environment.
Dr. Soneira used the following methods to test the true brightness of three handsets—the Samsung Galaxy S, the HTC Desire and the iPhone 4:
“I turned Auto-Brightness On and then measured the screen brightness (white Luminance cd/m2) that the iPhone 4 produces under a wide range of ambient light levels, from 0 lux (Pitch Black) up through 100,000 lux (Direct Sunlight). When Auto-Brightness is turned On the Brightness slider adjusts the Auto behavior to allow consumers (in principle) to set their own individual screen brightness preferences for ambient light. To evaluate this, I measured 5 different settings of the slider: Maximum, ¾, ½ (center), ¼ and Minimum. The results are plotted as the colored lines in Figure 1 – the circles are the measured data values.”
None of the auto brightness settings on the phone did what Dr. Soneira was hoping they'd do. The iPhone comes from the factory with the slider set to the center of the brightness scale, but at maximum brightness, auto-brightness only sets it to 60 percent of the maximum, which means that there’s 40 percent of the screen’s maximum brightness capacity that isn’t used. Dr. Soneira adds that, "at 10,000 lux, which is full daylight, the screen brightness is still below 90 percent of maximum. The ¾ setting is much too bright and power wasteful for all indoor viewing and yet it still throws away 20 percent of the screen brightness at 2,000 lux for outdoor viewing. The Maximum setting is useless because it varies the screen brightness (and power) by less than 10 percent and the ¼ and Minimum settings are far too dim to be useful for humans."
The biggest issue of the iPhone 4 is that its auto brightness function has a serious bug that locks the display onto the brightest ambient light sensor value, and then it continues to use that high value until the display is turned off through sleep mode or by powering it off. In that way, the display is set too high, which wastes power and causes severe eye strain once you enter a dark room. Auto-brightness should always adjust depending on the environment of your room, not the last environment it remembers.
It seems that despite the mobile operating system, Android couldn’t escape the shackles of a buggy sensor, either. The Samsung Galaxy S and HTC Desire only had four fixed screen brightness levels, essentially rendering auto brightness completely useless. Both Android phones had either ridiculously high or ridiculously low brightness levels, which means that if you’re in the market for an Android phone you might have to check out the manufacturer to make sure the display is up to par. 
From his study, Soneira concluded that automatic brightness is virtually useless because the software has absolutely no way for users to customize the display to their liking. All the mobile phones used in this study had some serious issues--most smartphones are operating without Auto Brightness because users disable them when they see that they don’t work. And when they do this, the screen is likely set to a very high screen brightness, which sucks the battery life of the phone.
Soneira concludes that right now, the user interfaces that handles the brightness control on these phones are completely backwards--the light sensor measures the ambient light, but then adjusts the screen brightness based on some odd algorithm set by a user setting that was initiated beforehand. The solution to this problem would be to completely reverse it and have the user adjust the screen brightness to whatever they want depending on the ambient lighting. So, if they enter a dark room, the phone will automatically adjust based on the user's settings, not what the factory recommends for the users.
Dr. Soneira also suggests that handsets have "a temporary Brightness Shift" that's fast, convenient and easy. The shift would enable smartphone users to have brightness controls available from their volume controls for just a short period of time, giving the user a few seconds to ponder how bright they want that screen to really be.
If those that make the mobile operating system could just figure out a way to give instant brightness adjustment to the masses, then consumers would have a comfortable viewing angle of their smartphones and wouldn’t have to worry about the battery dying halfway through the day. If all this could happen, then we could all just pretend like “Brightnessgate” never happened.
Check out the entirety of Dr. Raymond Soneira's article.