Channel Overlays

At the very bottom of the Curves dialog box in Photoshop CS3 are four new options that control what's displayed inside the grid area. The first one is Channel Overlays. Curves isn't used only for adjusting brightness levels in an image. It's also great at correcting color problems by allowing us to adjust the curve for each individual color channel. We've always been able to select individual color channels from the Channel option above the grid area, but we could only view the curve for a color channel when we had that channel selected. In Photoshop CS3, we can now view the curves for all color channels at once as an overlay when viewing the composite channel. Simply select the Channel Overlays option at the bottom of the dialog box (it's already selected by default) to view the overlay:

Unfortunately, we can't select any of the individual color channels in the overlay. We still need to select a color channel from the Channel option to make any changes to it.

To View Or Not To View The Histogram

If you find that the histogram makes the Curves grid area in Photoshop CS3 look too cluttered, you can hide it by unchecking the Histogram option at the bottom of the dialog box. Select the option again to turn the histogram back on:

Baseline

As you drag points around and reshape the curve in Photoshop CS3, you'll see a light gray diagonal line appear from the bottom left corner to the top right corner of the grid. This is known as the Baseline and it represents the starting point of the curve before any adjustments were made. The Baseline gives us a quick way to see what's happening with our adjustments. When working with brightness values, any areas of the curve that appear above the baseline will be brighter than they were originally, and any areas of the curve below the baseline will be darker. If you're working with ink percentages, the opposite is true. By default, the Baseline is visible, but if you'd prefer to hide it, simply uncheck the Baseline option at the bottom of the dialog box:

Intersection Lines

As you move a point from one spot to another, a horizontal and vertical line will appear that intersects at the point, helping to see exactly which brightness values you're selecting in the bottom gradient bar and where you're moving them to in the left gradient bar. If you'd rather not see the intersecting lines, uncheck the Intersection Lines option at the bottom of the dialog box:

Ready-Made Curves

Photoshop CS3 comes with a collection of ready-made curves that you can choose from to quickly lighten or darken an image, adjust contrast or create simple photo effects. You can access the list of preset curves from the Preset drop-down list at the top of the Curves dialog box. Click on the name of the one you want in the list to select it:

Saving Your Own Custom Curve Presets

If you've created a curve and you know you'll want to use the same curve with other images, there's no need to recreate it each time. Simply click on the icon directly to the right of the Preset option at the top of the dialog box and choose Save Preset from the list:

Give your custom curve a descriptive name (I named mine "Steve's Curve" but you may want to come up with something better), then click Save. As long as you saved your curve in the default location, your curve will now be available any time you need it along with the rest of the preset curves in the Preset drop-down list:

If you chose to save your curve somewhere else, you'll need to click back on the icon to the right of the list of presets and choose Load Preset, then navigate to the where you saved the curve to access it.

And there we have it! That's our look at what's new and improved inside the Curves dialog box in Photoshop CS3!