16th century Martin Luther paneled alum tawed binding. The top section of the photo shows the book under normal illumination. For the middle section the Diffuse Gain mode was used to illustrate the abrasion of the alum tawed. The bottom section again uses the Specular Enhancement mode to show the detail in the cover, in this case the “ID” in the center panel near the bottom of the close-up. Notice that this detail is virtually impossible to see under normal illumination.