User`s manual

Reference: The Advanced Image Correction Tools 71
The LCH Color Model
One of ScanWizard Pro’s strengths is its ability to let you work in the LCH
color space. Unlike the RGB color model, which corresponds to the color space
as defined in monitors and printers, the LCH color model is a more intuitive
way of working with colors, based on the values of Lightness (the “L” in LCH),
Chroma (C), and Hue (H). For instance, if you wish to change the color of the
sky in an image to a darker blue, your own eye — and your own judgment —
will be the guide to making those color changes. This is easier than, say,
knowing the mathematical equivalent in RGB or CMYK values that would
correspond to a “dark sky blue”.
The LCH model, in effect, makes it easier to comprehend colors as they are
couched in the terms we are familiar with: Lightness (how dark or light a color
is), Chroma or saturation (how rich or dull a particular hue of green is), and
Hue (the property that distinguishes, say, the color red from the color blue.)
In the LCH color model, colors of equal brightness lie on a single plane of the
model, as shown below. Red and green lie opposite each other on the horizontal
axis, as blue and yellow lie opposite each other on the vertical axis.
On the color sphere shown below, you can see how the different LCH properties
play out:
• The different hues (red, green, yellow, blue) are spread around the sphere.
• The chroma (saturation) for each hue increases from the center of the sphere
outward, with the most saturated colors lying on the edge of the sphere.
• The brightness values increase from the bottom of the model to the top.