I have images where there is a lot of "black" background (few shades of black). (In many images at least half the pixels are background). I need to get interest points from the image, but because the background is not smooth (although black) , I get a lot of "false" key points in the background. What filter/s will fit best to keep the details in the image but will smooth the background as much as possible ? I tried median filter, but the size needed to reduce background noise ([5 5]) was to strong for the small details in the image I wanted to keep sharp, same for Gaussian with very small sigma.