Gradation means gradation. Inimage processing and display, gradation refers to the reproduction behavior of graphics and photos with different tonal ranges. This is due to the fact that peripheral devices such as displays, projectors, imagesetters, printers and even the printer papers have different tonal value gradations.
The color representations and the brightness and contrast gradations are different for the mentioned devices. Since the impression of the tone value reproduction and the tone value change depends on the display, the projector or printer, this parameter can be changed by gradation curves. The corresponding adjustment is made by gamma correction.
Gradation curves reflect the density range of the image and are used to change the tone value. They can be used to influence the brightness, contrast and color contrast of the individual colors. By changing the slope of the curve and the shape of the curve, the distribution of the tonal values changes. This allows image values to be adjusted to the output values during image processing.