Contrast (1/4 and 3/4 Tone)

Contrast is controlled by moving the 1/4 and 3/4 tone points away from each other (increased contrast) or towards each other (decreased contrast).

 
 
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Move the 1/4 tone point down and the 3/4 tone point up to increase contrast.

Increase Contrast

While still in an Adjustment Layer Curves Dialog Box, adjust the 1/4 and 3/4 tones. Make sure the value readout is set to Ink Percentage. Make sure the Preview box is checked. Move the 1/4 tone point down and the 3/4 tone point up to increase contrast. Use the Kenly 3•6•9 Rule. You can check and uncheck the Preview box to see the effects of your 1/4 and 3/4 tone adjustments.

 

 
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Decrease Contrast

Move the 1/4 tone point up and the 3/4 tone point down to decrease contrast. Use the Kenly 3•6•9 Rule. You can check and uncheck the Preview box to see the effects of your 1/4 and 3/4 tone adjustments.

Click OK once you have set the 1/4 and 3/4 tones

 

Kenly 3•6•9 Rule

The Kenly 3•6•9 Rule gives guidance for adjustments in Curves. Developed by Eric Kenly, the rule states the following:

An adjustment of 3% is a minor correction.
An adjustment of 6% is a moderate correction.
An adjustment of 9% is a major correction.

Any adjustment over 9% suggests that the image should be recaptured.

These percentages work in both plus or minus ranges. Adjustments of +6% or -6% are both moderate.