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Chapter 5: Color Correction in the CMYK Color Space: Expert Mode
5-21
To illustrate how to work with gradation curves, consider this example: Suppose
your goal is to reduce the CMY values in the quarter tones. You would proceed as
follows:
1.
Select the Grad 3 radio button.
2.
Click on the quarter tone anchor point of the Grad 3 curve.
3.
Drag the anchor point down and monitor the numerical values in the table.
Note:
Very small changes in a gradation curve
shape can have dramatic effects.
4.
Update your image using the button at the top of the
CMYK Gradation window (or turn on automatic updating).
5.
Measure the density values in the image window using the CMYK Probe.
6.
Repeat steps 2 through 5 until you achieve the desired result.
Using Negative Slope Detection
At the top of the CMYK Gradation window is a section called Negative Slope
Detection. This feature is designed to limit the movement of the anchor points for
the Grad 3 and Grad 4 curves, preventing you from creating an invalid curve with
a negative slope (which occurs when a point on the curve goes above an anchor
point).
Setting the desired curve shape may involve moving multiple anchor points. If a
point has reached its maximum or minimum slope and no longer moves, nega-
tive slope detection is at work. It may then be necessary to adjust another point
on the curve so that the curve will move freely again.The default setting for nega-
tive slope detection is on (checkbox checked). If the function is off, all anchor
points move freely, but if a negative slope is detected in the Grad 3 or Grad 4
curve, the appropriate box is checked in the Negative Slope Detection section. The
image cannot be updated or final scanned until the negative slope situation is
corrected.
Summary of Contents for PowerColor
Page 7: ...Preface...
Page 8: ......
Page 12: ......
Page 13: ...Installation 1 1...
Page 14: ......
Page 21: ...Getting Acquainted 2 2...
Page 22: ......
Page 44: ......
Page 45: ...Correcting Images with PowerColor Photo RGB Mode 3 3...
Page 46: ......
Page 63: ...Correcting Images with PowerColor Press CMYK Production Mode 4 4...
Page 64: ......
Page 66: ......
Page 80: ......
Page 81: ...Correcting Images with PowerColor Press CMYK Expert Mode 5 5...
Page 82: ......
Page 106: ......
Page 107: ...Unsharp Masking and Descreening 6 6...
Page 108: ......
Page 116: ......
Page 117: ...Scanning Images to Disk 7 7...
Page 118: ......
Page 125: ...Tips and Tricks 8 8...
Page 126: ......