Black and white tones of photographic composition

Black and white tone refers to the general tendency of the relationship between image brightness in photographic composition, such as black and white photography. 0 degree can be used to represent black, and 10 degree can be used to represent white. After the image is illuminated by light, different light receiving surfaces form different shades of black and white, resulting in nine different brightness grays. In this way, eleven lightness series color scales from black to white can be obtained. Divide this lightness color scale into three sections, from 0 to 3 degrees, which are called low lightness areas; From 10 degree to 7 degree, it is called high brightness area; The middle part from 4 degrees to 6 degrees is called the middle brightness area. If the contrast difference is within 3 levels, we call it the weak brightness contrast (also called low-key contrast). The difference of brightness contrast is between 3 and 5 brightness levels, which is the middle contrast of brightness (also called midtone contrast). If the brightness contrast is different by more than 5 brightness levels, it is a strong contrast (also called high-profile contrast). Different lightness and hue give people different feelings. Such as: high-profile clear, open, clear, low-key plain, depressed; Low long tone and strong explosive force; Alto gives a fantastic impression. In photographic composition, different colors can be used to organize the picture relationship, which can constitute different effects of the picture.