التباين الناتج عن تأثير الإختلاف بين أصول الألوان ، في مقدار الأشعة المنعكسة منها

The contrast resulting from the effect of the difference between the color origins, in the amount of
The reflected rays are:

We will start first with a brief introduction to what we mean by "color origins". Colors, in a broad sense, are characterized by three characteristics that determine their color specifications. These three characteristics are:

(a) The origin of the hue: a property that is determined by the wavelength of the light reflected from the object. It is the property based on which we mention in our colloquial language that this color is red, green, blue, yellow... etc.

(b) The degree of saturation: Saturation or the degree of chroma: it is the characteristic that indicates the mixing of the original color with another neutral color that may be white, black, dark or light gray, and this adjective is based on which we mention in our colloquial language that this color Tinted or Shaded.

(c) Brightness or color value: it is. The property that depends on the amount of rays reflected from the origin of the colour. Assuming that there was a body that was originally red in color and we placed half of it under bright light (such as sunlight), and the other half in shade, then it is certain that the degree of brightness of the color differs in the two halves. Here it can also be said that the color value has changed in both halves, although A has not changed. The origin of the hue or the degree of its saturation.

Returning to the topic we are looking at, we say: Hues color origins do not reflect an equal amount of the rays falling on them even assuming that each of the values ​​and chroma degrees are equal and the color surfaces are in agreement. (As if all the colored surfaces were made of velvet fabric, for example, or were all made of leather, etc.) Some colors reflect a much different amount of radiation than other colors reflect, assuming that the amount of rays falling on them is equal. In support of the aforementioned facts, we mention in the following table the results of a series of experiments (1) conducted to measure the amount of rays reflected on surfaces that differ in their color origins and are similar in the type of surface material. .

Since these experiments were conducted under one light condition, it will also indicate that the amount of rays falling on the colored surfaces was equal as well, and therefore the previous colored surfaces did not differ except in one factor only, which is the origin of the hue color.

The Weston exposure meter was used to measure the amount of rays reflected from each colour. The readings he mentioned were in the second column of the tables. In order to make it clear to us the practical effect of the result of the difference in the amount of rays reflected from the original colors, we find in the last column of the table a statement of the diaphragm that ensures the correct exposure of each color separately, assuming that the shutter speed = 1 on the 25th of a second.