In comparison between the first two pictures look at how the highlights on the hills or top of ruffle add more realism. When ever you get stuck and don’t know where to go erase to add highlights, stand back a few feet and review. You should be able to notice how the highlights or whitest parts [top of hills] pop apart to form the ruffles.
I want you to notice where the pick arrow is there is a sharp contrasting line separating the fold. By pitting the dark next to the light charcoal value they will pop apart. The black arrow indicates “The top of the hill’ fold. Keep the tops of folds clean and highlighted.
Notice the curves of the folds or known to my students as Hills and Valleys. Top of hills are light where the valleys are darker in value. Remember the value scale and gradual transition of value in scales. Look at the value scale for one to ten values.