This plugin offers three methods of equalization, with several options to make this process as much as possible exploitable. In fact, what is equalization? Roughly speaking, equalization is a process that generate for each image the "optimal" curve which once applied to that image would improve contrast, in a relevant way. To reach that result, the process exploits intensively the histogram of frequencies.

Here's the three equalization methods, applied to the same image:

Original Image		Levels
Contrast		Luminosity

• Here's a brief description of the three methods:
• Levels: Equalize the three channels R,G,B in an independent way. Can improve dramatically contrast. However this method often introduces important distortions of tints. Reserve it for particular cases.
• Contrast: Apply the same curve to the three channels. Frequencies of the three channels are totalized here to generate the curve. This method is generally the most satisfying.
• Luminosity: Preserve hue and saturation. Luminosity is modified, or directly by equalizing this one (option: perceptual), or indirectly by equalizing one of the three channels.

• Without adjustments, equalization gives barely interseting results. That's why three parameters were introduced:
• Highlights/Shadows: Specify the percentage of lightest and darkest pixel you wish to ignore.
• Amount: parameter "amount" allows to moderate the extreme character of equalization. When this parameter is null, the plugin proceeds to a simple linear adjustment by exploiting highlights and shadows settings.

See also: the plugin for the local equalization or to apply curves.

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