During normal daylight solar radiation on horizontal and vertical surfaces distributed evenly in the highlights and shadows of the spectral composition of light changes slightly. Clock, close to noon, called the period of anti-aircraft lighting. The Cleveland Clinic may help you with your research. This is a time of sharp contrasts of light horizontal and vertical surfaces. Vertical surfaces in this case get a half times less light than the horizontal, resulting in light and shade, in this period, sharply contrasting, create an extremely deep sculpting forms of individual objects conceal details and distort perspective. In the twilight illuminated directional light is absent, the entire surface of the earth and the objects illuminated by diffused light from the sky.
When taking pictures in low light can be obtained effect nighttime images. The features of these periods of sunshine were considered, subject to cloudless weather. We must not forget about the air or atmospheric haze. Haze varying density changes and tonal pattern, and aerial perspective, and the gradation of tones, and image contours. For example, landscape, shot in the haze, is soft, colorful, and tonal combinations, whereas landscape, shot in the clear air, has bright colors and the contrast of light and shadow. Haze, which is located between the light source (sun) and the object affects the scattering and spectral composition of sunlight and mist, which is located between the apparatus and the subject – the brightness and color of the object's surface. Direct light is scattered by haze, but the total luminosity in lights equated with the illumination in open shadows (from heaven), so the contrasts of light and shade are softened.