Colour Grading: RGB and Hue Curves >

# Plotting Colour Values when Adjusting Curves

Plot the colour value of any sample on RGB and Hue curves. While you make adjustments, you can plot colours as often as necessary to isolate the colours you want to modify.

To plot colour values when adjusting curves:

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 final adjustments to the primary grade, click Output.
   - To make curve modifications for secondary colour grading, enable a secondary layer.
2. In the Player, sample the colour you want to use as reference. Click the image to sample a single pixel. You can drag through the image until you locate the pixel you want to sample, and then click.

   On the RGB curve, red, green, and blue vertical lines appear, representing the red, green, and blue colour channels.

   On the Hue curves, a single vertical line appears, representing the colour on the hue spectrum.

3. To zoom in on a curve using rectangle zoom, drag a selection box around the desired area while pressing Alt, and then release the mouse.

   The area of the curves contained by the selection box now occupies the entire Curve canvas.

4. To zoom in on a curve using proportional zoom, press Alt while dragging right or left with the right mouse button.

   The aspect ratio of the Curve canvas is maintained while zooming in and out.