An image processing system is disclosed which uses gain information from an input image to determine a threshold value used to filter the input image. The gain information is indicative of the amount of illumination of the input image and thus the noise level. The image processing system includes an image processor, a converter and a filter. The image processor receives and processes first image information into second image information and extracts the gain information from the first image information. The converter converts the gain information into a filter threshold, which is used by the filter to filter the second image information to provide filtered image information. The converter may include a lookup table storing noise characteristic estimates or the threshold values. The threshold values may further be based on subband size. The filter may be a wavelet-based transform denoising filter.