Gradationskurve

A gradationskurve, also known as a tone curve or gamma curve, is a graphical representation used in image editing and printing to describe the relationship between the input tonal values of an image and the output tonal values. It essentially maps how the brightness or color of each pixel will be adjusted.

The horizontal axis of a gradationskurve typically represents the original input values, often ranging from pure black on the left to pure white on the right. The vertical axis represents the output values, also ranging from black at the bottom to white at the top. A straight diagonal line from bottom-left to top-right signifies no change in tone; each input value is mapped directly to its corresponding output value.

By manipulating the shape of the gradationskurve, users can selectively adjust the contrast and brightness of different tonal ranges within an image. For instance, an S-shaped curve, where the middle section is steeper, increases contrast in the mid-tones while leaving the highlights and shadows relatively unchanged. Conversely, a curve that flattens out in the mid-tones will reduce contrast.

Gradationskurven are crucial tools for photographers, graphic designers, and printers to fine-tune the appearance of images, correct exposure issues, enhance detail, and achieve specific artistic effects. They allow for precise control over how light and shadow are rendered, impacting the overall mood and visual impact of a photograph or graphic. The concept is also relevant in display calibration and in the reproduction of colors.