Making Accurate Color Adjustments in Photoshop

By Simon Tuckett

Dateline: May 11, 2006
Version: Photoshop CS

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It’s difficult to read numbers in the Info palette while you are pushing curves or dragging sliders because moving the Eyedropper tool makes numbers disappear. Instead of wasting time going back and forth with the Eyedropper to get color readouts, ensure your color adjustments are accurate with the Color Sampler tool.

When a client asked me to replace the classic red of a tricycle with their corporate color, I started by creating a chip of the desired color next to the bike. I’ve reproduced the image with the corporate color chip for you. To follow along, download the 3 MB archive and extract the tricycle.psd file, shown at left.
Open tricycle.psd and follow my process by selecting the Color Sampler tool. (Press Shift-I until it appears in the toolbox.) Click once in the color chip to place a color sampler point—a crosshair and a number. Press Command/Ctrl while click-dragging a sampler point to move it around. If you make a mistake, Option/Alt-click the sampler to remove it. Now click in the flat, colored area at the back of the tricycle seat for a second color sampler point. (You can place up to four points in an image.) Placing a color sampler point automatically expands the Info palette, and you’ll see readouts corresponding to your two points. Notice the readouts are in CMYK, but by clicking an eyedropper to the left of a readout, you can change it to RGB, Grayscale, or another option such as Total Ink. Control/Right-click on a color sampler point to access a contextual menu with some additional options.
I’ve already created a selection of the tricycle’s red areas for you, so select the Target chip layer, move to the Paths palette, and Command/Ctrl-click the Red Regions path to load it as a selection. Create a Hue/Saturation adjustment layer by clicking the Create new fill or adjustment layer icon at the bottom of the Layers palette. In the resulting dialog box, you’ll notice that as you drag the Hue/Saturation sliders, the Sampler 1 readout numbers do not change. The Sampler 2 readout displays two sets of numbers: The original values and the adjusted values. Your job is to bring the values for Sampler 2 closer to Sampler 1. Start by dragging Hue all the way to the right, decrease Saturation to –60, and click OK.

Duplicate the Hue/Saturation adjustment layer by pressing Command/Ctrl-J. Now choose Layer > Change Layer Content > Curves. Press Command/Ctrl-1 to access the Cyan channel. Reduce the amount of ink by dragging the curve down about 3/4 of the way across the grid until the Cyan value of Sampler 2 in the Info palette matches the Cyan value of Sampler 1. Access the Magneta channel by pressing Command/Ctrl-2, but this time push up the curve until you match the Magenta value of Sampler 2 with the Magenta value of Sampler 1. After pressing Command/Ctrl-3 to access the Yellow channel, drag the curve down slightly to match the Yellow value of Sampler 2 with the Yellow value of Sampler 1. The tricycle now matches the target color, but it appears flat. To create the wider range of values evident with metallic paint, add a bit of contrast to the image in the form of another adjustment layer or a slight S-curve on the Black plate of the Curves adjustment layer.

Make a habit of arranging the order of your readouts the same way each time. For example, I make Sampler 1 the target color and Sampler 2 the color to be adjusted. When necessary, I use Sampler 3 to evaluate light areas and Sampler 4 for dark areas.

In the absence of a calibrated monitor and a color management system, matching color to a predefined color chip is remarkably accurate. In CMYK, the numbers don’t lie. If you have to match a given color, find the number of a PMS color that matches it, and place a chip of that color in the document. Use the color correction tools to modify the document’s color until it matches with the color chip.

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Simon Tuckett is an illustrator and retoucher based in Toronto.