Patent ID: 7352398

Claim:
An image pick-up apparatus comprising: image pick-up means for picking up images of the same object a plurality of times under different exposure conditions to generate images corresponding to a plurality of pictures with different exposure values; image synthesis means for synthesizing the images corresponding to the plurality of pictures to generate one synthetic image in which luminance values of respective pixels are represented by a first number of gradations; histogram detecting means for detecting a histogram indicating frequency distribution of luminance values of the synthetic image; gradation number converting means for converting the number of gradations of the synthetic image into a second number of gradations to generate an output image in which luminance values of respective pixels are represented by the second number of gradations, wherein according to a conversion rule based on a synthetic function, into which a linear function determined based on a ratio between the number of gradations of the synthetic image and the number of gradations of the output image and a histogram function having a characteristic corresponding to the histogram are synthesized, the gradation number converting means converts luminance values of respective pixels represented by the first number of gradations into luminance values represented by the second number of gradations; and extracting means for extracting luminance components of the synthetic image and delivering the components to a gradation correction circuit, wherein the gradation correction circuit converts the luminance components into a predetermined value based on the classification of the images for the synthetic image.