THE OVERCAST DAY, A TIME of cloudiness and no great sunshine, has taken on a negative connotation in human affairs. Yet it may be one of the best times to paint out of doors, which seems contrary to everything artists learn.
Many painters and photographers go for the sunrise or sunset period. The light comes in at an angle, giving definition to terrain and other objects. A time like this provides the lightest lights and, by the contrast effect in the eyes, the darkest of darks. Furthermore, in painting at such times, the questions about the direction of light are all answered. And one can often assume the sunrise light is yellowish, the sunset light reddish.
Not so when the day is overcast. In ways, an overcast time of day sets up something akin to “tonalist" painting, which uses middle to dark tones only to create its special mood and effect. In painting outdoor topics, that means that the tonalist seeks the gloom of twilight, typically.
By contrast, an overcast day is backed by the full light of the sun. In this case, though, the light is diffused by the cloudy atmosphere. Light is spread evenly and subtly. The visual result is that colors are not washed out by the exceedingly bright rays of the sun. Colors can become richer, not duller, though their intensity has been subdued.
The proof in this pudding is the array of such paintings that have come down to us.
One good example is the American painter William Merritt Chase (1849–1916). Besides his many studio works, he produced a variety of landscapes, often with this overcast effect. A few from Central Park in New York City are typical, and there are others. Though the paintings of the sky might range from muted blue, to clouds and pure grey, the light on earth was diffuse, casting only soft shadows, if any. The range of tones are close, but the colors rich.
There are several ways to get the overcast effect.
As noted, one is to keep the value range fairly close, avoiding high contrasts of dark and light. Overcast days produce shadows, but they are diffuse. A painter can soften a shadows edge or even get away with barely a shadow at all. The same goes for objects: Softer edges on them can suggest a more all-around lighting.
While in strongly lighted paintings—of sunrise, noon, or sunset—shadows are a key way to define objects in the scenery, the opposite approach tends to apply to overcast days. Here, the objects themselves tend to provide the contrast and definition. Without much shadow to define them, trees, buildings, or human forms can almost be dark, middle-tone, or light in their entirety. This solidity of each form often allows for the rich use of color, since it does not have to show a range from darkest to lightest in one place, of one color, on one object.
Since landscape usually involves green, one standby helps create the overcast effect. This is by combining Ultramarine Blue and Yellow Ochre. The latter warms the former, but avoids the acidy feel that some green paint can create (such as Viridian). This blue-and-ochre mix, tinted with a bit of white, captures many of the greens in nature under its diffused light.
Clouds and water vapor in the sky are what diffuse the sunlight, and this also makes the light cool, as in a bluish cast. The coolness generally affects the color temperature of objects in the painting, and so also whatever shadows appear. The old rule seems to apply: object under cool line cast warm shadows. This is not hard and fast, but in its subtlety, it is a good rule of thumb—even if the best painter’s eyes do extract this fact of “cool objects, warm shadows” from a complex landscape itself.
Another approach I've seen is to mix up a particular gray color and divide it into three or four different values, dark to light. The trick here is to add the appropriate amount of gray to every pure color that is used. The effect is to subdue all these pure colors uniformly, capturing, when successful, the same uniform effect of diffuse sunlight.
Be forewarned, however. Overcast does not men “sunblock.” A long spell under the overcast sky not only suggests cool light and warm shadow, but also the refined rays of the sun, diffuse as they are, providing a health sunburn, nice and evenly done.