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.

To use the single channel Correction Curves in SoftRIP, select the Correction Curves option from the Color menu on SoftRIP's main screen. Select the Correction Curves you want to adjust and then select the particular color channel you want to edit in the Colorant area. Remember that only the areas of the image that are in the color space you have selected will be affected.

When using SoftRIP's Correction Curves, you have your choice of curve editing models: Light or Dot %. Prior to editing, the spline curve in the box is a diagonal line running from the bottom left to the upper right of the grid. One or more control points may be selected at any point along this line and dragged in any direction. Dragging a point up or down lowers or raises the output density at that point. Because the tone range is a continuum, whatever adjustments you make at one control point will affect the shape of the rest of the curve, and consequently, the values at all points along the curve. The advantage of the Correction Curves tool is that you are able to fine-tune a curve shape to control the color balance of an image.

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


Correcting RGB Images

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.

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