An exposure compensation method automatically generates an accurate exposure value to clearly show the profiles of objects in front of a black background or a white background. First, initial edge energy is derived from luminance values for pixels in a digital image having an initial exposure value. Maximum edge energy is obtained by varying an exposure compensation value for the digital image, and an optimal exposure compensation value according to the maximum edge energy is also obtained. If a difference between the maximum edge energy and initial edge energy is larger than a threshold value, a current exposure value is set to the initial exposure value compensated by the optimal exposure compensation value. Otherwise, the initial exposure value is directly designated as a current exposure value.