AmphiSoft Photo Sharpen 1.22

What is that "halo" were talking about? Halo appears when traditional sharpening filter meets, say, dark object on light background. In attempt to make image look sharper, that is, to improve local contrast along the edge, filter makes background area along the edge even lighter, while making object edge darker, thus introducing colors outside original image tonal range and forming noticeable halo along the edge.