I love to share these these drawings by Georges Seurat with my class when we learn about Tonality. Seurat is the artist most associated with Pointillism, that off shoot of Impressionism. But his drawings offer a subtle insight into the technique of rendering form only through value shifts, or tonality. Notice the complete lack of contour lines!
MoMA has put together a really nice online version of their 2008 Exhibition of Seurat’s drawings. http://www.moma.org/interactives/exhibitions/2007/seurat/
Enjoy! If you want to learn more about these techniques, join the Drawing Workshop!
See some tonality drawings from my students in the Drawing Workshop: HERE