In a recent painting of mine, you can see the sky and clouds are the lightest
While my subject matter of late has been the light as it falls on the human figure, I am equally interested in values as they are occur in outdoor landscapes. A personal goal of mine has been to learn to draw the human figure in the landscape. The same principles apply to both subject matters, of course, but with landscape the most common light source is the sun, or according to John E.Carlson, in his book, Carlson's Guide to Landscape Painting, the sky.
When outdoors we cannot control our light source in the same manner we can in the studio. The sun's light is absorbed and altered by clouds and moisture in the atmosphere, ever changing the landscape below. It moves across the sky and sometimes trees or other objects block the direct light from hitting the ground. It sets in a glorious array of light reflecting off of clouds at the sea's horizon, or can drop behind mountains rising high in the sky. The one constant is that the light never stops changing.
In the landscape, as in the studio, the angle of the light hitting a form is largely responsible for the value of the form. To simplify, an artist can divide the outdoors according to major planes, including the sky, the trees, the mountains, and flat ground. Again, simplifying, the lightest value is the sky–the source of the light.
This is true regardless of whether it is a clear or cloudy day. On a cloudy day, the clouds absorb the light, keeping the clouds lighter and the ground darker than it would otherwise be. The light that would hit the earth planes is blocked or obscured. The second lightest major form is the ground. This is the case regardless of whether the ground is comprised of flowers, or grasses, or other objects. You may see modulations in value as the lighter or darker color of hills and valleys emerge, but on balance they are of the same or similar value. Or at least they need to drawn or painted that way to avoid looking spotty, confusing the value relationships in the drawing or painting.
| This painting by Scottish nineteenth-century artist M.R.G. Coventry
has been in my family for a very long time. The sky is light in value
even though cloudy, and the land mass in the very front is light as
well. The rocks and tree in the background are quite dark, both
reflecting the fact that they are in shadow and that the angle of the
light is obtuse. The sea is lighter as well, reflecting the sky.
The third lightest plane is the diagonal or slanted plane such as that represented by large hills or mountains, which receive some light but not as much as the flat lying ground. The trees, perpendicular to the sky, are the darkest forms as they receive the least light. As is the case with undulations on the ground, the tops of trees receive more light than the undersides, but need to be represented by color changes more than value changes to avoid the spottiness that can otherwise result.
Architecture is much like trees. Tall, vertical buildings are often closest to the sky, but the light hitting their side planes is generally less direct than the light that hits their roofs.
Don't take my word for this. These are generalities, but if you spend time outdoors observing, you will see that these generalities are often true. My practice has been to observe, observe, observe. You will start to notice both the generalities and the exceptions to these, and see that knowledge in your paintings. I know it has helped me think about how to make a landscape painting look "natural" to a viewer.
Make charcoal sketches and paintings in values of gray, too. It is my observation that a drawing or painting holds up if the values are right, whether for a landscape drawing or studio painting or anything in between.