How to Grade Midtones in GIMP Color Balance

This guide explains how to use GIMP's Color Balance tool to color grade photographic midtones precisely while preserving deep shadows and bright highlights. By selecting the correct tonal range and enabling luminosity protection, you can shift the mood of your image through the midtones without crushing your blacks or blowing out white details.

1. Select the Midtones Range

Open your image in GIMP and navigate to Colors > Color Balance....

At the top of the dialog, find the Select Range to Adjust section. Choose the Midtones radio button. This setting focuses your adjustments strictly on the middle gray values (roughly the 25% to 75% luminance range). The tool uses a smooth falloff curve, meaning the strength of your color adjustments naturally tapers off as values approach pure black or pure white, leaving extreme shadows and highlights intact.

2. Enable "Preserve Luminosity"

Check the Preserve luminosity box located at the bottom of the Color Balance window.

When you add or subtract color channels, brightness values naturally shift. Enabling "Preserve luminosity" ensures that adding color to the midtones does not artificially brighten or darken those pixels. This prevents midtone color adjustments from spilling over into overexposed highlights or underexposed shadows.

3. Adjust the Color Sliders

With Midtones active and Preserve luminosity enabled, adjust the three primary color sliders:

  • Cyan / Red
  • Magenta / Green
  • Yellow / Blue

Shift these sliders in small increments. Moving a slider toward a warm tone (like Red or Yellow) or a cool tone (like Cyan or Blue) alters the ambient color grade of subjects and backgrounds without tinting the darkest black points or specular highlights.

Strict Isolation via Luminosity Mask (Optional)

While the Color Balance "Midtones" setting naturally tapers toward extremes, it still applies a fractional adjustment to near-shadows and near-highlights. If you require zero adjustment to shadows below 20% luminance or highlights above 80%:

  1. Duplicate your layer.
  2. Create a Midtone Luminosity Mask or use Select > By Color / Quick Mask to isolate only the exact midtone range.
  3. Apply the Color Balance adjustments through that mask to completely protect the extremes.