3A

Auto-Exposure:

AverageBrightness = c * Aperture * ExposureTime * AnalogGain * DigitalGain

c: a constant

Aperture: the size of the aperture of the len

Exposure: the time per frame each pixel in the sensor is expoed to outside lighting

AnalogGain: the gain applied to the analog pixel signal before A/D happens in the sensor

DigitalGain: the gain applied to the pixel signal after A/D

Priority must be given to determine which parameter shall be adjusted first:

Aperture -> Exposure time -> Analog gain -> Digital gain

Auto-White-Balance:

Statistical models are obtained from a large number of images taken under different illuminations. From these statistical models,key features are abstracted and saved in the camera's on-board ISP to enable real time estimation of the scene illumination.(Based on the statistics)

Auto-Focus: