A method of controlling a display parameter of a mobile device, the mobile device comprising a display, an ambient light sensor and a color light sensor, and a first imaging unit comprising a processing unit, the first imaging unit and the display being substantially in a same plane, the method comprising, when the display is positioned and oriented by a user, such that the display and the first imaging unit face towards the user's eye, wherein the position of the user eye is a reference position, performing by the mobile device the steps of: - obtaining a first image generated by the first imaging unit, - calculating a first light level from the first image, wherein the first light level is indicative of a first fraction of incident ambient light which illuminates the reference position after specular reflection of the incident ambient light at the display, wherein the calculating a first light level from the first image comprises the steps of: - determining from the first image a relative angle of the reference position with respect to the plane of the display (10; and a relative distance (d) between the reference position and the display, - determining a set of specular reflection vectors (P2r, P3r, P4r, P5r) by means of back-tracing rays of incident ambient light connecting the reference position and a set of reflection points (P2, P3, P4, P5), respectively, wherein the reflection points (P2, P3, P4, P5) are determined as corner points of a reflection area defined within a plane of the display, respectively, the set of specular vectors being determined based on coordinates of the reflection points, and the relative angle and relative distance of the reference position, - determining from the specular reflection vectors (P2r, P3r, P4r, P5r) an illumination region within the first image from which incident ambient light illuminates the reference position by means of specular reflection of the incident ambient light at the display, wherein the illumination region corresponds to a sub-region within the field-of-view of the first imaging unit from which ambient light reaches the reference position, and - calculating the first light level by integrating image values over the illumination region, wherein the method further comprises either the steps of: - obtaining from the ambient light sensor a first sensor signal indicative of the ambient light incident on the ambient light sensor, - determining a second light level from the first sensor signal, - adjusting the display parameter depending on the first and the second light level (L1, L4), the display parameter being a display brightness; or the steps of: - obtaining from the color light sensor a second sensor signal indicative of a color of ambient light incident on the color light sensor - determining a third light level from the second sensor signal, and adjusting the display parameter depending on the first and the third light level (L1, L5), the display parameter being a color white balance and/or a color point. - obtaining a first image generated by the first imaging unit, - calculating a first light level from the first image, wherein the first light level is indicative of a first fraction of incident ambient light which illuminates the reference position after specular reflection of the incident ambient light at the display, - determining from the first image a relative angle of the reference position with respect to the plane of the display (10; and a relative distance (d) between the reference position and the display, - determining a set of specular reflection vectors (P2r, P3r, P4r, P5r) by means of back-tracing rays of incident ambient light connecting the reference position and a set of reflection points (P2, P3, P4, P5), respectively, wherein the reflection points (P2, P3, P4, P5) are determined as corner points of a reflection area defined within a plane of the display, respectively, the set of specular vectors being determined based on coordinates of the reflection points, and the relative angle and relative distance of the reference position, - determining from the specular reflection vectors (P2r, P3r, P4r, P5r) an illumination region within the first image from which incident ambient light illuminates the reference position by means of specular reflection of the incident ambient light at the display, wherein the illumination region corresponds to a sub-region within the field-of-view of the first imaging unit from which ambient light reaches the reference position, and - calculating the first light level by integrating image values over the illumination region, wherein the method further comprises either the steps of: - obtaining from the ambient light sensor a first sensor signal indicative of the ambient light incident on the ambient light sensor, - determining a second light level from the first sensor signal, - adjusting the display parameter depending on the first and the second light level (L1, L4), the display parameter being a display brightness; - obtaining from the color light sensor a second sensor signal indicative of a color of ambient light incident on the color light sensor - determining a third light level from the second sensor signal, and adjusting the display parameter depending on the first and the third light level (L1, L5), the display parameter being a color white balance and/or a color point.