Differing values create contrasts that can affect the mood and composition of a drawing. The more extreme the difference between values, the greater the contrast. One way to achieve higher contrast in your drawing is to place your darks and lights side by side.
It’s All Relative
Value contrasts are relative. They appear differently according to their environment. The small square on the far left may appear darker than the small square on the near left, but both are the same value. The square on the left appears darker because it is placed directly against the pure white of the paper, providing more contrast.
Value Contrast Creates Impact
A drawing done without much contrast will not have much impact and will look flat and pale. The white smoke of the rocket on the right looks brighter against the dark background. The drawing on the right uses richer values, creating more contrast.