An image processing apparatus comprising: image-capturing-mode selecting means for selecting one image-capturing mode from a plurality of image-capturing modes; signal-value-region setting means for setting a predetermined signal-value region on image signals input from an image-acquisition element; noise-level calculating means for calculating noise levels; noise-reduction processing means for performing noise reduction processing on the input image signals on the basis of the noise levels; and a reference-noise-model storing portion for storing a plurality of reference noise models determined in accordance with the properties of the image-acquisition element; wherein each reference noise model indicates a relationship between signal value and noise level, and has a characteristic such that the noise level increases with an increase in the signal value; characterized in that the signal-value-region setting means set a signal-value region as the predetermined signal-value region, signal values of which are at or below a threshold determined in association with the image-capturing modes, in the case, where an image-capturing mode selected by the image-capturing-mode selecting means is a specific image-capturing mode; wherein the noise-level calculating means is configured to calculate a noise level of the signal-value region other than the predetermined signal-value region, on the basis of the reference-noise-model, and a noise level of the predetermined signal-value region, on the basis of an applied noise model, which is modified so that the noise level of the predetermined signal-value region is higher than the noise level of the reference noise model corresponding to the image-capturing modes selected by the image-capturing-mode selecting means, in the case, where the predetermined signal-value region is set by the signal-value-region setting means, and wherein the noise-level calculating means is configured to calculate a noise level of the entire region of the input image signals on the basis of the reference-noise model in the case, where the predetermined signal-value region is not set by the signal-value-region setting means. image-capturing-mode selecting means for selecting one image-capturing mode from a plurality of image-capturing modes; signal-value-region setting means for setting a predetermined signal-value region on image signals input from an image-acquisition element; noise-level calculating means for calculating noise levels; noise-reduction processing means for performing noise reduction processing on the input image signals on the basis of the noise levels; and a reference-noise-model storing portion for storing a plurality of reference noise models determined in accordance with the properties of the image-acquisition element; wherein each reference noise model indicates a relationship between signal value and noise level, and has a characteristic such that the noise level increases with an increase in the signal value; characterized in that the signal-value-region setting means set a signal-value region as the predetermined signal-value region, signal values of which are at or below a threshold determined in association with the image-capturing modes, in the case, where an image-capturing mode selected by the image-capturing-mode selecting means is a specific image-capturing mode; wherein the noise-level calculating means is configured to calculate a noise level of the signal-value region other than the predetermined signal-value region, on the basis of the reference-noise-model, and a noise level of the predetermined signal-value region, on the basis of an applied noise model, which is modified so that the noise level of the predetermined signal-value region is higher than the noise level of the reference noise model corresponding to the image-capturing modes selected by the image-capturing-mode selecting means, in the case, where the predetermined signal-value region is set by the signal-value-region setting means, and wherein the noise-level calculating means is configured to calculate a noise level of the entire region of the input image signals on the basis of the reference-noise model in the case, where the predetermined signal-value region is not set by the signal-value-region setting means.