HSL Curves

HSL Curves let you adjust relationships between hue, saturation, and luminance along a continuous curve. They might look familiar to you from video color grading apps, tuned here for photographic work.

You’ll find them inside Curves, alongside RGB and the individual color channels. On Mac, Curves uses a stack of expanding panels; on iPhone, the channel picker on the left scrolls so every HSL curve stays reachable.

Like RGB Curves, each HSL curve shows a relevant histogram behind it, so you can see the color or tonal distribution you’re shaping.

The HSL Curves tool in Darkroom showing the eight HSL curves

The curves

  • Hue vs Hue remaps one color range into another. The default tracks map to the same eight channels as Color, but you’re not constrained to Color’s definition of “blue” or “green.” You can work across neighboring hues with more range, for example dragging greens all the way to red for an infrared film look.
  • Hue vs Saturation changes saturation by color. Same starting channels as Color, with more range and the ability to work across multiple hues at once: calm a saturated sky, or add vibrancy to a hue that Color’s buckets treat too broadly.
  • Hue vs Luminance brightens or darkens specific colors. Lift or deepen a hue family without a global exposure change: deepen blues in water, or lift foliage.
  • Saturation vs Saturation has saturation on both axes. Desaturate highly saturated colors, or increase the vibrancy of desaturated ones. It’s useful when making presets for bright, colorful scenes or more somber ones, where loud colors might feel out of place.
  • Luminance vs Saturation has luminance on the x-axis and saturation on the y-axis. Control saturation based on how dark or bright a color is: desaturate bright regions, and increase saturation in the shadows.

When to use HSL Curves vs other tools

There’s some overlap with tools you already know:

  • Color (HSL) is still best for quick bucket edits with simple sliders.
  • Color Range masks are best when the change needs to stay local.
  • Color Grading is best for overall mood across shadows, midtones, and highlights.
  • HSL Curves are for the moments in between: more continuous and precise than Color, without needing a mask.

A useful order: set white balance first, use the Color tool for color broad edits, reach for HSL Curves when you need finer spectrum control, then finish mood with Color Grading if you want it.

Tips

  • Make small moves. HSL Curves are powerful, and big bends can shift neighboring colors in ways that look unnatural.
  • Watch skin tones carefully as they usually live in orange/red ranges and are easy to overcook.
  • Use the curve histogram as a guide displayed in the background of the curve: work where the photo actually has color information.
  • Pair with the main Histogram when you’re also balancing exposure and clipping.

Related

  • Curves (RGB) — tonal curves, points on and off the track, and channel picker
  • Color (HSL) — quick per-color bucket adjustments
  • Color Grading — mood by tonal range
  • Masks — local color and tone control