Color Manipulation Tips and Tricks: Curves

All About Curves
Using curves in Photoshop CS4 for prepress production can be intimidating to newbies so here are a few tips to help make color manipulation with curves a more enjoyable experience.

Display Options for Curves
If a Curves Adjustment layer is targeted in the Layers panel, selecting the flyout on the Adjustments panel reveals the "Curves Display Options". Here, you can choose to show your numeric values on a scale from 0-255 (light) or 0-100% (ink), Channel Overlays, Histogram, Baseline and Intersection Line.

Adding a Point on a Curve
With the On-image tool selected on the Curves Adjustments panel (that's the one that looks like the hand with the up/down arrow), hovering the cursor in the image area will display a preview circle (bouncing ball) over the corresponding value on the curve.
• Click in the image area to add a point to the curve.
• Click and drag up/down in the image area to add a point on the curve to lighten/darken the targeted value or
• Use the up / down or left/right arrows to move the selected point. (Add the shift key to move it in larger increments.)

Selecting Points on a Curve
With the On-image tool selected on the Curves Adjustments panel, Shift + (plus) will select the next point on the curve and Shift + (minus) will select the previous point.  Shift -click multiple points on the curve to select more than one and move them all at once. Command + D will deselect all selected points.



Deleting Points on a Curve
To delete a point on a curve, select the point and do any of the following:
• Press Delete/Backspace
• Command + click on point (on the panel or from the image area)
• Click and drag the point off of the grid

Curves Grid Preference
In the Adjustments Panel, Option-click in the grid area to toggle more/less grid lines. (10% vs quarter-tone increment)

Adding Color Samplers in Curves
When the Curves Adjustments panel is active, shift-click in the image area to set a Color Sampler. Shift -drag to reposition the Color sampler. Option + Shift-click on sampler to delete it.

Hope these tips help you to gain photoshop enlightenment. Using curves for color manipulation is one of the best ways to control color in your images. An even better way is with camera raws non-destructive color manipulation! Does it get better than this? I think not.

xxjoy