Working in sunny weather is one of the most challenging tasks for a painter. This is due to the enormous tonal range produced by sunlight.
Our world is three-dimensional, and light on volumetric objects is distributed very unevenly: one side can be dazzlingly lit by the sun, while the other is plunged into deep shadow.
The tonal difference between the brightest sunlit planes of objects and the deepest shadows in hidden areas easily reaches a ratio of 1000:1 or more. This creates a huge tonal range that our painting, being a flat two-dimensional surface, simply cannot replicate.
Unlike a volumetric tree or bush in nature, a painting cannot simultaneously contain areas brightly lit by the sun and areas immersed in deep shadow. The tonal range of our paints is much narrower than that of nature.
However, by adjusting the exposure of the tool, it is possible to significantly expand the tonal range of paints to match the scene (with the exception, of course, of sun glare or clouds).
To expand the brightness range of paints, the scene should be conventionally divided into several tonal zones — for example, three main ones: lights, midtones, and shadows. For each of these zones, the "exposure" of light on the tool is adjusted separately.
When comparing with the light areas of the scene, the tool’s blade is turned directly toward the sunlight. This allows the paint on the tool to reflect the maximum amount of light, making it possible to correctly match the brightest tones of the scene.
To match midtones, we lower the exposure on the tool by slightly turning it away from direct sunlight. This creates lighting conditions on the paint surface that better correspond to the midtones in nature.
Finally, to match the color of shadows, we reduce the light exposure on the blade even more. Under such conditions, the paint on the tool appears significantly darker.
At the same time, a desirable effect occurs — in order to match the natural shadows, the painter will automatically need to lighten the paint on the palette, which helps avoid creating dead, "black hole" shadows in the painting.
A short rule for painting in sunlight is this: the lighter the object being painted, the more light should fall on the blade.
Of course, with this kind of dynamic matching, some manual adjustment of tonal relationships will inevitably be needed in the actual painting. But the hue and saturation of the color are captured very accurately in such comparisons.
Thus, working in sunlight using the method of direct comparisons is difficult but possible — at least for accurately checking color and saturation.
An exception remains when the subject of the painting is backlit relative to the artist. In this situation, direct color matching is difficult because the tool itself is in shadow.
However, there is a proven solution for this: the scene can be photographed, and the work can then continue in the studio using the photo or a computer screen. Under these conditions, the palette can reliably and accurately cover the entire tonal range of the scene, since a photograph or screen compresses the full tonal range to a level suitable for working with paint.