HSLcurves

HSLcurves refer to a method of color adjustment that uses separate transfer curves for the Hue, Saturation, and Lightness components of the HSL color space. By shaping these curves, an editor can modify color relationships, intensity, and brightness in a coordinated yet flexible way.

The core idea is to map each channel’s input value to a new output value through a curve. For Hue, the curve defines how input hues shift around the color wheel, potentially wrapping around 360 degrees. For Saturation, the curve controls how vivid or muted colors become as a function of their original saturation. For Lightness, the curve determines how bright or dark tones shift across the image. In practice, curves are constructed from control points and interpolated, often using monotonic or smooth Bezier-like transitions. The processing can be applied by transforming RGB data into HSL, applying the curves, and converting back, or by applying the curve adjustments directly in a color-managed pipeline such as a LUT.

Applications of HSLcurves include color grading, photo retouching, and cinematic color workflows, where precise, non-linear control over hue, saturation, and lightness allows for targeted tonal shaping and mood creation. They are frequently implemented in non-destructive editors, enabling adjustments to be revised or removed without altering the original image.

Limitations include potential artifacts if curves are too aggressive, the need to handle hue wrap-around gracefully, and the dependency on the chosen color model. HSLcurves are often used in conjunction with other color tools for comprehensive tonal control.

See also: color grading, curves, HSL color space, LUTs.