Sävykäsittelykurvet

Sävykäsittelykurvet, often translated as tone curves, are a fundamental tool in image editing used to adjust the brightness and contrast of an image. They represent a graphical method of manipulating the tonal range of a photograph. The horizontal axis of a tone curve typically represents the input tonal values, ranging from pure black on the left to pure white on the right. The vertical axis represents the output tonal values, also from black at the bottom to white at the top.

A straight diagonal line from the bottom-left corner to the top-right corner signifies a linear relationship, meaning no tonal adjustments are being made. By clicking and dragging points on this curve, users can selectively alter specific tonal ranges. Lifting a point on the curve in a particular region increases the brightness of the corresponding input tones, while lowering a point decreases the brightness. This allows for precise control over highlights, midtones, and shadows.

Steeper slopes in a section of the curve indicate increased contrast in that tonal range, while flatter slopes reduce contrast. For example, creating an "S" shape by lifting the midtones and highlights while lowering the shadows will generally increase overall image contrast. Conversely, a reversed "S" shape can decrease contrast. Tone curves are a powerful and versatile tool for photographers and graphic designers to enhance image appearance, correct exposure issues, and achieve specific artistic looks. They are found in most image editing software, including Adobe Photoshop, GIMP, and Affinity Photo.