Split Toning in GIMP Using the Curves Tool

Split-toning is a color grading technique that infuses different colors into an image’s highlights and shadows, commonly used to create a cinematic look. This guide explains how to use GIMP's Curves tool to map cool blue tones into your shadows while adding warm golden hues to your highlights, all within a single adjustment interface.

Step 1: Prepare the Image and Open Curves

  1. Open your image in GIMP.
  2. In the Layers panel, right-click the base layer and select Duplicate Layer so you can adjust opacity later.
  3. With the duplicate layer selected, navigate to the top menu and select Colors > Curves....

Step 2: Add Blue to the Shadows and Yellow to the Highlights

  1. In the Curves dialog, locate the Channel dropdown menu at the top (which defaults to "Value") and switch it to Blue.
  2. Cool the shadows: Click on the bottom-left point of the diagonal line (representing shadow tones) and drag it upward slightly. This injects blue directly into the dark areas of the image.
  3. Warm the highlights: Click on the top-right point of the curve (representing highlight tones) and drag it downward. Reducing blue in the highlights reveals its complementary color, yellow.
  4. Add an anchor point near the center of the curve line and drag it back toward the diagonal baseline to keep your midtones relatively neutral.

Step 3: Enhance the Warmth with the Red Channel

  1. Change the Channel dropdown from "Blue" to Red.
  2. Warm the highlights further: Click slightly above the midpoint along the upper-right section of the curve and pull it upward. This adds red to your highlights, blending with the previously added yellow to form an orange tone.
  3. Cool the shadows: (Optional) Click on the lower-left section of the line and pull it down slightly. Reducing red in the shadows introduces cyan, reinforcing the cool, moody shadow effect.

Step 4: Balance Tint with the Green Channel

  1. Switch the Channel dropdown to Green.
  2. If the shadows look overly cyan or green, pull the lower-left area of the curve down slightly to introduce a subtle magenta tint to balance the cool tones.
  3. If the highlights look too red or orange, push the upper-right area up slightly to shift the warmth toward a softer yellow.

Step 5: Adjust Contrast and Apply

  1. Switch the Channel dropdown back to Value.
  2. Create a subtle S-curve by dragging the lower third down and the upper third up to restore contrast that might have softened during the color grading.
  3. Click OK to commit the changes.
  4. Go to the Layers panel and lower the Opacity of the edited layer if you want a more subtle, natural look.