1. A circuit for photographing an image to obtain a first frame and a second frame and detecting a flicker by using the first and the second frames, the circuit comprising: a luminance average value output unit for extracting luminance values from pixel data of the first and the second frames to generate first luminance average values for pixel lines of the first frame and second luminance average values for pixel lines of the second frame; a flicker curve generating unit for subtracting the second luminance average values from the first luminance average values, thereby generating a flicker curve; and a flicker detecting unit for extracting a plurality of local minimum points from the flicker curve, calculating a distance between each two neighboring local minimum points of the extracted local minimum points, and determining whether the flicker is present based on the distances and the frequency numbers of the distances.