DisplayMate Head Explains Why Auto-Brightness Schemes on Smartphones Suck

Paul Lilly

Dr. Raymond M. Soneira, President of DisplayMate Technologies, has never been one to mince words when it comes to holding display maker's feet to the fire. He's made a name for himself by shattering myths perpetuated by those whose jobs it is to hype and market LCD panels of all shapes and sizes, an attitude that meshes well with our "Minimum BS" motto. So when Dr. Soneira told us he wrote a lengthy piece on why existing brightness controls and light sensors in today's displays are effectively useless -- particularly on the iPhone, Android devices, and HDTVs -- we took a coffee break to read what he had to say.

"Although consumers currently don't pay much attention to them, the Automatic Brightness control and LIght Sensor on smartphones and HDTVs has a major impact on displayed image quality, screen viewability, and readability, as well as preventing eye strain and headaches when the screen is too bright or too dim for the current level of ambient lighting, which varies considerably," Dr. Soneira explains.

According to Dr. Soneira, "most smartphones and HDTVs run with the screen considerably brighter than it should be, which wastes a lot of power in addition to causing eyestrain." Throwing some hard numbers into the mix, Dr. Soneira points out that HDTVs use as much as 75 percent of the total TV power, which oftentimes translates to over 200 watts. With 330 million TVs in the U.S. alone beaming content 600 billion hours per year, "that adds up to a considerable amount of wasted energy, money, and oil."

Because of this, one would think smartphone and HDTV makers would pay particular attention to automatic brightness schemes, but according to Dr. Soneira's extensive lab testing, that isn't the case. Not by a long shot.

But before delving into what's wrong, it's important to understand how automatic brightness schemes work, at least in principle.

"Both smartphones and HDTVs have a light sensor located in the bezel right next to the screen that measures the ambient light together with control software that appropriately raises or lowers the screen brightness based on the measured light level," Dr. Soneira says. "If you are watching in the dark the screen should be appropriately dim. When the ambient light level is higher the screen needs to be made appropriately brighter for two reasons: because of glare from ambient light reflected off the screen, which washes out the image, and because the eye’s light sensitivity decreases substantially as the ambient light level increases. Unfortunately, none of the above currently works properly in smartphones and HDTVs."

Why not? According to Dr. Soneira, one easily avoidable problem is the placement of the light sensor. He argues that by placing the light sensor facing forward, all it's doing is measuring the brightness of your mug rather than the true ambient lighting that's behind and on either side of the phone or HDTV. He also argues that whatever algorithm display makers are using, they should scrap it. During his real-world test cases, Apple's iPhone 4 did a terrible job automatically the adjusting the brightness based on lighting conditions.

"It certainly looks as if no one at Apple ever bothered to set or check Auto Brightness for useful performance, which is why there are lots of user comments questioning how it works on the Web," Dr. Soneira says.

Android fans don't have any room to gloat, because the situation is even worse on phones built around Google's open-source platform.

"There are currently a large number smartphones running Google’s Android OS, and all of the models that we have looked at appear to work in the same way," Dr. Soneira explains. "There is a slider for manual adjustment of screen brightness, but when Automatic Brightness is enabled the slider disappears and there aren’t any user settings or preference adjustments (unlike the iPhone 4) –- you get whatever screen brightness settings Android and the smartphone manufacturers have pre-programmed into them. Unfortunately, those Automatic Brightness settings are incredibly primitive and crude."

What's more, both Android phones Dr. Soneira tested -- Samsung Galaxy S and HTC Desire -- exhibited auto brightness errors, or bugs, where the brightness levels ended up being set "ridiculously high."

Dr. Soneira didn't just set out to bitch and moan about how careless smartphone and HDTV makers are when it comes to auto brightness schemes, he also proposed a novel solution. In short, Dr. Soneira says an intelligent algorithm that essentially records and learns what brightness levels users prefer in various lighting conditions could then be set to optimal levels at all times, based on the user's veiwing habits.

To read the full report -- and there are quite a few details we've left out -- head over to www.displaymate.com/AutoBrightness_Controls_2.htm .

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