How to Paint Moonlight
To learn how to paint moonlight, let's first look at the light that we are dealing with. The light from the moon is a weaker source than the sun causing the light to appear cool to our eyes. Unlike the sun, there is usually no reflected light. Although, in some instances snow will cause some reflected light on a clear night with a very bright moon. The value range in a moonlit scene is diminished to about two thirds of the spectrum. Colors become grayer and cooler. And, edges are softer.
Toward the foreground the colors will become more saturated and closer to their local color. There is a multitude of grays in a moonlit scene and the darkest darks can be either warm or cool. Generally, the colors that are exposed to the light of the sky will be cooler than their local color. The rule lights are cool and shadows warm applies here. Black can be mixed with colors to gray them, but don't use black in itself. There are subtle differences in colors.
If you are painting the moon itself, the color is not just white. It can appear a bluish color, yellow, orange or pink and will vary slightly in values over the surface. The moon will also have a glow around it, causing the sky to appear a green color from the yellow or a reddish color, depending on the color of the moon. The sky can vary from a bluish dark to a violet. If there are city lights, the horizon will pick up some of the warm lights in the color.
Remember that the moon light is directional. So, the sky can vary in color and value and an object will show the source of light with varying values and slight temperature changes. But, it is all very subtle in a moonscape.
Below are some paint swatches in bright daylight. I took the same swatches and manipulated them in photoshop, making the value range less and darker. I cooled the colors with blue and made the colors less saturated. This will give you some idea what moonlight will do to the colors. This is just a generalization and certainly not true for all night scenes or all colors in the same painting.
The blog, Illustration Art has a post about Remington's night scene paintings.
As far as equipment, I use two clipon booklights, one on the canvas and one on the palette. I have found that at times I have to turn them off for a while, especially on bright moonlit nights. Sometimes it is easier to see the values comparing them with the lights off. And always, I need to check the painting the next day. Sometimes, it's a surprise.
Nocturne in Blue and Silver: The Lagoon, Venice ,1879-1880 by James Abbott McNeill Whistler. Oil on Canvas. Museum of Fine Art, Boston.
James Abbott McNeill Whistler