An apparatus comprising: a processor configured to control a flash unit in an exposure time period (T 1 ) of a rolling shutter image sensor array , wherein the processor is configured to: receive information indicative that there is a requirement for electrical energy other than by the processor and flash unit , determine whether an intensity of ambient light is above or below a threshold light intensity, control, responsive to determining the intensity of the ambient light is above the threshold light intensity, the flash unit to provide light over a time period (T 1 ) that is substantially equal to the exposure time of all image sensor elements of the rolling shutter image sensor array, control, responsive to determining the intensity of the ambient light is below the threshold light intensity, the flash unit to provide light only over a time period (T 3 ) that is common to exposure time periods of a plurality of rows of image sensor elements of the rolling shutter image sensor array , and control the flash unit in the respective time period (T 1 , T 3 ), using the received information, to: provide a first non-zero light intensity in a first portion of the respective time period (T 1 , T 3 ) and to provide a second non-zero light intensity, different to the first light intensity, in a second portion of the respective time period (T 1 , T 3 ); wherein the first non-zero light intensity is higher in intensity than the second non-zero light intensity; and wherein an electrical energy storage device is configured to provide: a maximum current output to the flash unit during the first portion of the respective time period (T 1 , T 3 ), and an intermediate current output to the flash unit during the second portion of the respective time period (T 1 , T 3 ). receive information indicative that there is a requirement for electrical energy other than by the processor and flash unit , determine whether an intensity of ambient light is above or below a threshold light intensity, control, responsive to determining the intensity of the ambient light is above the threshold light intensity, the flash unit to provide light over a time period (T 1 ) that is substantially equal to the exposure time of all image sensor elements of the rolling shutter image sensor array, control, responsive to determining the intensity of the ambient light is below the threshold light intensity, the flash unit to provide light only over a time period (T 3 ) that is common to exposure time periods of a plurality of rows of image sensor elements of the rolling shutter image sensor array , and control the flash unit in the respective time period (T 1 , T 3 ), using the received information, to: provide a first non-zero light intensity in a first portion of the respective time period (T 1 , T 3 ) and to provide a second non-zero light intensity, different to the first light intensity, in a second portion of the respective time period (T 1 , T 3 ); a maximum current output to the flash unit during the first portion of the respective time period (T 1 , T 3 ), and an intermediate current output to the flash unit during the second portion of the respective time period (T 1 , T 3 ). <EOS>