COLOR CORRECTION

CORRECTING HUE USING SINGLE CHANNEL CURVES

Single channel editing is generally used to change the hue or color balance of photo images, which are usually in RGB mode, or the shade of vector art or spot colors which are usually in CMYK mode.

In order to use the Single Channel correction curves in SoftRIP, go to the Correction Curves option of the Color menu and select the correction color space in the Processing Step area. Select the mode (either RGB or CMYK) under the Source heading, and then select the particular color channel you want to edit in the Color Channel area. Remember that only the areas of the image that are in the color space you have selected are affected.

When you move control points on the curves up, whether RGB or CMYK, the "amount" of that ink color will increase proportionally (when using the Dot% model). When you move the control points on the curves up, the amount of that ink color will increase proportionally. The location of the control points you select will affect that part of the tone range for that particular color, but will also affect the rest of the curve to a lesser degree. By experimenting with multiple control points and varying curve shapes, you can gain a great deal of control over the color balance of an image.

Using single channel curves in the
Dot% mode to adjust the magenta channel.

Correcting RGB photoimages
Note that each CMYK primary color name on the interface is accompanied in parentheses by its complementary RGB primary color. Whether you are most comfortable making color corrections in RGB or CMYK, the fact remains that RGB and CMY are theoretically two sides of the same color space. This means, for example, that if you increase the yellow density by pulling the control points down, you are simultaneously decreasing blue density. To most effectively adjust hues in RGB images, you will need to think in terms of the RGB primaries when making these adjustments. For our purposes here, the most important concept underlying single color curve corrections is that any change you make to one color channel affects other color channels. Changes to any single color also affect the overall lightness or darkness of the image.

In terms of using the curves in daily practice, keep this principle in mind: if you need to make extreme changes in a particular hue, it is better to move the dominant channel curve a little in one direction, and the other two in the opposite direction.