Merits -Phong shading or Normal Vector Interpolation Shading
Hence by finding intensities at various points across the edge we determine the intensity that is varying across the edge among two vertex points and is not uniform like in Gouraud Shading, providing much good effect. Thus we can say as the normal vector interpolation by Phong shading is better to intensity interpolation method as in Gourand Shading since it largly reduces the mach bands.