What determines the success or failure of a silhouette is the graphic design of the elements in the composition. Kudus are large African antelopes, and they make great silhouettes because of the curvature of their elegant horns. The shape of the animal in this shot plus the shape of the acacia tree made a strong combination of elements, and the sunset glow added a great backdrop. I saturated the colors in Adobe Camera Raw for additional visual impact. I took this with a 500mm Canon telephoto, and my settings were 1/250, f/8, and 1600 ISO. I was using a bean bag to support the camera and lens which meant I turned the image stabilization off to prevent blurred pictures.