Working in sunny weather is one of the most challenging tasks for an artist. This is due to the colossal tonal range that the sun creates.
Our world is three-dimensional, and on volumetric objects, light is distributed extremely unevenly: one side may be glaringly illuminated by sunlight, while the other is immersed in the deepest shadow.
The tonal difference between the brightest surfaces of objects facing the sun and the deepest shadows in sheltered spots can easily reach proportions of 1000:1 or more. This creates an enormous tonal range, which our painting, being a flat, two-dimensional surface, simply cannot replicate. Unlike a volumetric tree or bush in nature, it cannot simultaneously have areas brightly lit by the sun and areas immersed in the deepest shadow. The tonal range of our paints is much narrower than that of nature's colors.
However, thanks to the adjustable exposure setting of the tool, it is possible to significantly "compress" the tonal range of nature to a level acceptable for our paints (except, of course, for sun glare or clouds).
To narrow the brightness range, it is useful to divide nature into several tonal zones — for example, into three main zones: light, midtones, and shadows. For each of these areas, we adjust the "exposure" of light on the tool separately.
When we compare with the lighter areas of nature, we position the blade of the tool as much as possible 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 in nature.
To match the midtones, we reduce the exposure on the tool by slightly turning it away from direct sunlight. This creates lighting conditions on the paint's surface that are more consistent with the midtones found in nature.
Finally, for the shadows, we reduce the exposure of light on the blade to a minimum. Under these conditions, the paint on the tool will appear significantly darker.
The desired effect occurs: to match the shadows in nature, the artist will automatically have to lighten the paint on the palette, which prevents the creation of dull, "black hole" shadows.
The simple rule here is this: the lighter the object we are painting, the more light should fall on the blade.
Of course, with such dynamic adjustments, some "manual" correction of tonal relationships will inevitably be needed in the actual study. But the actual hue and saturation of the color, when using such comparisons, are captured very well.
Thus, working in sunlight with direct comparisons is difficult but possible. The exception is when the painting subject is in backlight relative to the artist. In this situation, direct color matching is complicated because the tool itself ends up in the shadow.
However, there is a proven solution for this as well: one can photograph the subject and work in the studio from the photograph or from the computer screen. In these conditions, our palette will reliably and accurately cover the entire tonal range of the scene, as the photograph or screen compresses the tonal range to a level that is acceptable for working with paints.