Using GIMP: Correcting and Touching Up Your Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 128

2.5.11 Overview of some of the
Functions in the Colors Menu

Menu Function Explanation

Color Balance Used to adjust colors in an image and to modify

color levels of red, green, blue, cyan, magenta, and
yellow. Each correction can be done separately for
different ranges of brightness (Shadows, Midtones, and
Highlights). Also used to correct images with color cast.

Hue-Saturation Hue: Changes colors in relation to each other. Provides

limited possibilities for correcting colors, including
images with color cast. Suitable for graphical effects
and the distorting or colorizing of image elements.
Saturation: Increases or reduces the saturation
(intensity) of an image's colors (up to gray levels).
Lightness: Lets you additionally adjust the lightness
of an image. But keep in mind that this is not a tool like
Brightness-Contrast, used to correct the luminosity
and the contrast of an image. When Lightness is
adjusted with the Hue-Saturation function, the image
is uniformly darkened or brightened to black or white.
You can decide whether changes will apply to all colors
of an image or a specific color only.

Colorize Renders the image as a grayscale image as seen

through a colored glass.

Brightness-Contrast Sets the brightness and/or contrast (light-dark

distribution) of an image.

Threshold Lets you set a threshold between black and white

image sections, which serves as the value from which
the image is converted into a pure black-and-white
image.

Levels (tonality correction) Lets you adjust the light-dark distribution in an image
(together with the color extent and contrast). Creates
real new shadows and highlights (black-and-white
tones) in an image. It can also be used to correct the
brightness of an image by adjusting the midtones.
Each color channel can be modified separately.
Provides an option for automatically setting the levels.

Curves (gradation curves) Lets you adjust color curves, similar to Levels and

Brightness-Contrast but with a purely graphical
interface for the settings. You can use this function to
achieve inverted and graphical distortions similar to
solarization.