An apparatus and method for processing an image of an image signal projected through a digital camera lens are provided. The apparatus includes an image sensor module for transforming an optical signal into an electric signal, to generate and output an image signal, and a light receiving module for detecting a light source. The apparatus also includes a light source characteristic detector for detecting a frequency of the light source, a white balance controller for controlling a white balance, a color corrector for removing interferences of red, green, and blue channels, and a gamma corrector for performing a gamma correction. The apparatus further includes an auto color adjustment controller for identifying a kind of light source based on the frequency of the light source, and controlling a white balance gain of the image signal based on the kind of the light source.