How Apple Crafted the iPad Pro’s True Tone Display

True Tone puts the new iPad Pro's screen ahead of Apple's other touchscreen devices Apple

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Apple’s 9.7-inch iPad Pro is the company’s one-two punch — a tablet that can, in boxing terms, float like a mid-sized machine and sting like a pro computer. Our review of the smaller iPad Pro revealed that it’s hard to outright replace your desktop with it. But it remains the best iPad you can get your fingers on, acting as the culmination of everything the tablet edition of iOS has to offer. As well as one, so-far unique feature: True Tone.

The iPad Pro 9.7 is the first—and probably not last—iOS product to offer this technology, which uses the ambient light of whatever surroundings the iPad is in to determine the balance of colors onscreen. The brighter display and wider color gamut lead to a better experience, according to Apple. But the key to the new feature is how the company retooled of the device’s ambient light sensor.

An ambient light sensor has been part of every iOS device since the first iPhone was released in 2007. It’s what allows the screen of your device to automatically lighten or darken depending on the level of surroundings. But what the company hoped to achieve with True Tone was something greater than detecting how bright surrounding light was: a way to accurately take in the colors of your surroundings as well. “We found out no such sensor exists, so the team had to create one,” said an engineer involved with the project who preferred to remain anonymous.

True Tone is similar to another color-shifting feature in newer iOS devices called Night Shift. Similar to the app f.lux before it, whites become more warm in hue as it gets later in the day. While some evidence supports that Night Shift is better for one’s REM cycle, nothing objectively says True Tone is easier on your eyes. But the effect is along the lines of what our eyes are used to. Similar to how our brains consider the page of a book white regardless of if we’re under a clear blue sky or yellow desk lamp. The effect of True Tone is seamless when turned on and very noticeable when switched off.

In addition to crafting the upgraded ambient light sensor, the company made sure it was being tested properly. Apple confirms they created their own database of lighting combinations—light bulbs, shades, tinted windows, etc.—in writing the True Tone algorithm. The number of light combinations ranged in the thousands.

The challenge then was making sure the proper results were repeatable and mass-producible for all the sensors going into the numerous iPads that needed to be shipped. To address this, engineers created a t machine which emulates different light sources to ensure every iPad measured light and accurately adjusts colors. The result is the upgraded ambient light sensor included in the iPad Pro 9.7-inch model. Similarly-sized to the one we’ve known from the other iPads, but much more capable in detecting light color and intensity.

Apple won’t say whether or not we’ll see the new ambient light sensor make its way to the next iPhone, other iPads and potentially even Mac laptops. But a device’s screen remains integral to the computing experience and Apple’s already extended their pixel-packing, Retina-display fervor to nearly every product type in their lineup. iPhone users will have to wait until later this year to find out if True Tone will migrate to their new phones.