In some implementations, a mobile computing device may participate in the calibration of an output signal of a media device. This calibration process includes storing device-specific calibration data which is related to properties of a light sensor of the mobile device. The mobile device then detects of properties of light emitted by the display device during a presentation to obtain sensor values related to light emitted by the display device during the presentation. The calibration process may also ensure that the mobile device is proximate to the display device prior to obtaining the sensor values. The collected sensor values are adjusted using device-specific calibration data stored to the mobile device to normalize the sensor values relative to a baseline. These normalized sensor values are sent to the media device for use in adjusting the output signal based on the normalized sensor values.