By their very nature landscape paintings generally contain mostly land in the division of space in the painting. Usually less than a third of the canvas area is reserved for the sky. This seems to confuse most people when they start painting and they ignore what they see and paint what they think they know. What they think they know is the sky is blue and so it has to be a deep saturated blue in my painting.
This causes problems for the rest of your painting, because the sky, more than anything else is the key to how the light in the painting is behaving. Get the sky color wrong and you ruin the sense of light in the painting. If we examine the area of sky that is actually in the painting we will find for the most part it is made up very little blue if any. The blues that are there tend to be very high key, with lower saturation than at the skies zenith. So what is going on here?
Well, if you measure the relative size of visible sky included in your painting you will find it is barely above the horizon line. All of that blue sky you are looking at has no place in your painting if this is the case. The sky just above the horizon is affected by dust and clouds and rarely presents the deep blue of the zenith. At the lower levels toward the horizon the sky leans toward a greenish blue depending on the meteorological conditions. This is especially true in the summer when the air is warmer and the angle of the sun higher. In winter the lower sun angle and cooler air offer more opportunities for a clear blue sky.
Painting outdoors offers the artist a unique chance to observe these affects firsthand. When painting from nature it is important to leave your preconceived ideas at home and be open to the experience. This is especially true when including skies in your painting.
