لون أشعة ضوء النهار .. كتاب الإضاءة والفلم

Daylight color:

the color of the daylight rays and the geographic country (with respect to latitude and longitude or with respect to elevation above sea level) changes; The color of the rays also changes between sunrise and sunset, but may also change at one hour according to the clear blue color of the sky or overcast with clouds and clouds.

And when we mention that the color of the rays has changed, this means that one of the colors that make up the white rays (such as the red color for example) has increased in proportion to what reaches us to the ground in the place of imaging, and there is no doubt that the increase in the proportion of this color indicates a decrease in the proportion of The other parts that make up the white rays. If the percentage of red rays increases, this indicates a decrease in the percentage of blue or green rays (for any of the reasons that we will mention in this chapter).

The rays of the day tend to redden with yellow during the sunrise period, then this redness gradually decreases as time progresses until it becomes white or close to white in the middle of the day. At the end of the day, when the sun begins to set, its color develops towards redness again, and the redness reaches its maximum degree in the moments when we see the sun close to the horizon line while it is setting.

This phenomenon is not due to the fact that the light energy emitted by the sun itself has changed its properties, but rather to the fact that some of the blue rays that are part of the composition of the sun's rays have been scattered during their passage through the atmosphere surrounding the earth, as a measure of dust and water vapor is attached to it. They would absorb some of the short-wave visible rays (blue and violet), and thus increase the proportion of the other longer-wave rays, namely red and yellow (Fig. 9), and this is the reason for the redness of the color of daylight at sunrise and sunset hours (Fig. 10).

It follows from the change in the color of the sun’s rays during these hours that the colors of the bodies do not appear to be faithfully transmitted if they are photographed with color film at these times. For this reason, it is not recommended to photograph outdoors with color film until two hours after sunrise or at least two hours before sunset, unless we intend to do so. did that
For a special purpose or effect that we want in the image, then it will be covered with a warm color (1) red that tends to yellow.

But what colors would we expect in the image if filming was done with color film at these times? To answer that, we say that people’s faces will be covered with an orange tinge resulting from the redness of the rays with their yellowness, as for blue and green colors (such as trees and some flowers or some parts of the sky) their saturation will decrease (2) Desaturated, as red or yellow rays (complementary to them) are added. Complementary) their colors are Neutralized (i.e. their color becomes neutral gray), in other words, the degree of purity of the colors decreases, as the colors of the green trees appear in the picture as if they were mixed with a dark gray color (3) As for the yellow or red colors in nature, they will be covered with a new tinge of reddish tinged yellowing (4).