To use the values in painting, let's keep it simple creating a painting with three shapes of varying sizes. Now, use three values, light, medium and dark. Each of those three shapes have a distinct value. But, you can have an infinite variety of color within each shape.
Once you start painting different values within a shape, you start breaking that large, simple shape into small pieces. Each of the three shapes should be a different size. If you make your largest shape a dark value, the painting will have a different mood and feeling than having that same shape in a light value.
So, you must be careful or you will soon lose the power of your composition. Be consistent with your values within those simple, large shapes to hold your composition together. I used a "real life" painting that demonstrates the simplicity of shapes and values. This is a plein air painting in which I made the decision to move the trees and group them into one large, dark shape. I placed them against the light of the mountain in the background.
By making these changes, my painting has a better composition than what I saw in reality. I do have color shifts in the trees and mountain with warmer and cooler colors, but basically I kept those large shapes intact with the values. Below is the color version of the painting so that you can see the color shifts and variety of colors in the shapes. In the grass I have bits of violets, pinks, greens, golds and yellows, creating a visually more exciting painting, but again, keeping those values consistent.
I hope this post gives some clarity to the use of shapes, values and colors. What do you think? How have you used values? Have you changed your subjects to unify your paintings? Becky Joy