Using the Calibrate Controls
Now you're ready to tweak the calibrate controls to fine-tune the color, so select the Calibrate tab by clicking its label (or press Command-4 on Macs, Control-4 on Windows). Figure 7 shows the controls in the Calibrate tab.

Figure 7: Camera Raw's Calibrate tab

The Shadow Tint slider controls the green-red balance in the shadows. Negative values add green, positive values add red. Check the darkest patch on the target in the raw image. If it's significantly non-neutral, use the Shadow Tint control to get the R, G, and B values to match as closely as possible -- normally, there shouldn't be more than 1 level difference between them.

The final adjustments are to the Red, Green, and Blue Hue and Saturation controls while sampling the red, green, and blue patches on the target. This can be a little counter-intuitive at first. When you work on the red patch, you'll find that the Red Hue and Red Saturation controls don't change the red value for the red patch. Instead, they adjust blue and green relative to red. The Red Hue control adjusts blue and green relative to each other, changing the hue, while the Red Saturation control changes blue and green by equal amounts relative to red, increasing or decreasing the saturation -- higher amounts of blue and green make a less-saturated red, lower amounts make a more-saturated one. That's why you made that final saturation move in the Adjust tab.

Each edit you make inevitably has some impact on the other colors, so it's important that you start with the green patch, then the blue, and finally the red. If you make the edits in this order, you'll find that the low blue value for the blue patch gets increased, and the high red value for the red patch gets reduced.

Start with the Green Saturation, and get approximately the right proportion of red and blue to green for the green patch, then use the Green Hue control to get the right mix of red and blue relative to each other. Typically, you'll bounce back and forth between the hue and saturation controls three or four times. Repeat the process for the blue patch next, and finish with the red. When you nail the relative hue and saturation of these three patches, the other color patches pretty much fall into place. Figure 8 shows the edited capture, and the Calibrate tab edits.

Figure 8: The edited capture (top), and the Calibrate settings that created it (bottom).

Saving your Settings
Once you've done the work, you'll want to save the Calibrate settings so that you can apply them to images that are more interesting than captures of Color Checkers. To do so, choose Save Settings Subset from the Camera Raw menu, then, in the ensuing dialog box, choose Calibration Only -- that way, you can apply the Calibration settings to other images without interfering with any other edits you made to them.

Figure 8: The Save Settings Subset (top) with the Calibration Only choice selected (bottom).

If you normally save settings to sidecar .xmp files, save the Calibration setting in Camera Raw's Presets folder (Adobe Photoshop CS> Presets> Camera Raw) so that they'll always be available. If you normally save the settings in the Camera Raw database, you don't need to do anything special to make them available at all times.

You'll probably have to make separate Calibrate settings for daylight/strobe and for tungsten, but the daylight settings will work for just about anything other than images shot under actual tungsten light. In particular, they don't lock you in to the white balance and tonal adjustments you made to the target. They simply tweak the performance of the built-in profiles to better match your camera, so you'll still enjoy the freedom Camera Raw offers in interpreting white balance and tonality. You'll just get more accurate hue and saturation relationships in your images.

I've tested this procedure on about a dozen different cameras, and by investing about 10 minutes on each unit I've been able to dial in the color in Camera Raw so that each one produces near-identical results. So if you like the idea of Camera Raw, but you've been wrestling with skin tones that are too red, skies that are too green, or color that just isn't quite right, maybe it's time you too paid a visit to the Calibrate tab.

Read more by Bruce Fraser.