Colour Grading: RGB and Hue Curves > Modifying Red, Green, and Blue Channels > Modifying Hue, Saturation, Luminance, and Lightness >

# Modifying Image Luminance

The Luminance curve represents the gamut of light from black to white. Use the Luminance curve to saturate or desaturate different luminance areas by adding or removing hue from black and white points. Like any other curve, you can add points to refine ranges of an effect.

To suppress or saturate luminance areas in the image:

1. Indicate the colour grading stage at which the curve modification is being applied:
   - To work on the initial primary grade, click Input.
   - To make curve modifications for secondary colour grading, enable a secondary layer.
2. Click Hue and then click L-S to display the Luminance curve.

   The Luminance curve is plotted to the hue spectrum.

3. Sample the luminance areas you want to use as a reference for your adjustments. See Plotting Colour Values when Adjusting Curves.

   A vertical line representing the reference colour is plotted on the Luminance curve.

4. To select a vertex, click it. To select several vertices, draw a selection box around them.
5. Saturate or suppress the luminance area:
   - To saturate the luminance area displayed in the hue spectrum, drag selected vertices up.
   - To suppress the luminance area displayed in the hue spectrum, drag selected vertices down.

   Tip You can also select a vertex to use tangent handles to adjust the curve.
6. To move several selected vertices, select them and then drag one. To restrict vertex movement to the Y axis, press Shift while moving the mouse. To restrict vertex movement to the X axis, press Shift+Alt.
7. To add a vertex to the curve, place the cursor over the area on the curve where you want to add the vertex and then press A. To lock the curve in place while adding a vertex, press Shift+A on the curve.
8. To delete vertices, select them and then press D.
9. Edit the curve until you are satisfied with the results.