A portable electronic device includes a housing, a front cover defining a front side of the portable electronic device, a display stack below the front cover and comprising a plurality of display layers configured to produce a graphical output in a display region of the display stack, the graphical output visible through the front cover, and a light sensor module positioned at least partially within the housing and coupled to the display stack in the display region. The light sensor module may be configured to receive ambient light passing through the front cover and through the plurality of display layers and, while a blanking interval is positioned over the light sensor module, produce an output corresponding to the received ambient light, the portable electronic device configured to determine an ambient light value based at least in part on the output from the light sensor module.