Adding a fourth value, a light gray that is inbetween the medium gray and white, allows further distinctions. The cloth is now light gray, rather than white, in its lightest areas. The white highlights on the peppers are now the only white areas in the picture, so they stand out more as a result. Some of their edges, however, are softened by a few small areas of light gray that bridges the white part of the highlights with the medium gray of the peppers.