Apple pointed out in a newly released support document that MacBook Pro 2018 has True Tone technology that also affects external screens. The 2011 Thunderbolt display and LG Ultrafine devices also adjust their white point when connected to the new MacBook Pro.
If you connect the new MacBook Pro with its TrueTone display to some external displays, you’ll benefit from its white point adjustment. Activating this mode under macOS is possible with a simple checkbox. The system automatically adjusts all compatible displays accordingly. Currently, it is not clear if the function works when the computer is in “clamshell” mode – closed.
True Tone technology was first introduced to the Apple world with the 9.7-inch iPad Pro and ensures that the white balance of the display remains the same for the user, regardless of the ambient light on the screen. When the device is moved from one environment to another, color rendering is always perceived by the user as “equal.
How True Tone affect external displays?
When ambient light changes, the white balance and general color scheme of the screen normally appears to change, even if the display settings remain the same. This is actually a problem caused by the user’s own view, as he observes the change in other lighting conditions in the environment and adapts to them. However, it also notices an apparently changed display setting
True Tone solves the problem by using four-channel sensors to detect the ambient light that can affect the display’s perception. If a change is detected, e.g. when the user moves an iPad Pro on a sunny day from a room lit with cool lamps into the more yellow light outdoors, the screen automatically changes its display so that the screen remains comparatively unchanged despite the different lighting situations.
Probably either the Thunderbolt port or the USB 3.1 Type C port on the new MacBook Pro provides additional information to the display to allow these changes that do not allow HDMI or DisplayPort.
The LG UltraFine 4K display, developed in partnership with Apple, and its larger 5K sibling model were launched in October 2016 for the redesigned MacBook Pro. The displays serve as a replacement for Apple’s Thunderbolt Display, which was discontinued in June 2016.