Patent ID: 8285041

Claim:
An image processing apparatus comprising; a histogram computing section which computes a histogram of pixel values of input image data; a gradation conversion characteristic determining section which determines a gradation conversion characteristic in a case where gradation conversion processing is applied to the input image data, on the basis of the histogram computed by the histogram computing section and information on noise characteristics which indicates what degree of noise is added, and in what form, when the input image data has been picked up; and a gradation converting section which converts the gradation of the input image data on the basis of the gradation conversion characteristic determined by the gradation conversion characteristic determining section, wherein the gradation conversion characteristic determining section further comprises a histogram correction section which, when determining the gradation conversion characteristic, calculates a reciprocal number of a noise quantity after gradation conversion from a default gradation conversion characteristic using the information on noise characteristics, and corrects a portion of a frequency value in the histogram which exceeds the reciprocal number of the noise quantity after the gradation conversion to be limited to the reciprocal number of the noise quantity after the gradation conversion, and wherein the information on the noise characteristics includes the noise quantity which varies in accordance with an image pickup sensitivity, a temperature or an exposure time when the input image data has been picked up.