Info Palette
The Info palette is a great resource for showing you color values, measurements and other information that can be surprisingly useful if you know what to do with it. Although you can't actually choose a color by using the Info palette, you'll find it helpful for measuring the colors that already reside in your document. The top part of the Info palette measures the color that appears below your cursor.
You can change the measurement method used by the Info palette by clicking the tiny Eyedropper icons within the palette (Figure 1.38). RGB is usually used for desktop printing and multimedia purposes, while CMYK is usually reserved for images that will be printed on a printing press. Total Ink adds the C, M, Y, and K numbers to indicate how much ink coverage will be used to reproduce the area under your cursor.
Figure 1.38. Changing how the Info palette measures color.
Most images opened in Photoshop contain 256 shades of gray, or 256 shades each of red, green, and blue (also known as 8 bits per channel). Many photographers are starting to use 16-bit images, which can contain up to 32,768 shades of gray, or shades of red, green, and blue. If you're working on a 16-bit file, then you can see 16-bit numbers (0–32,768) instead of the standard 8-bit numbers (0–255) in the Info palette. Do this by clicking on the tiny eyedropper icon in the Info palette and choosing 16-bit (in CS, choose Palette Options from the side menu of the Info palette and turn on the Show 16-bit Values check box.) I don't find this to be all that useful, but you're welcome to try it if you're a bona-fide numbers geek.
You can set up the Info palette to keep track of different areas of your image, so you can see what's happening when you make adjustments. You can do this by clicking your image using the Color Sampler tool (hidden under the Eyedropper tool). This will deposit a little crosshair on the area you click, and will also add another readout to the Info palette (Figure 1.39). You can add up to four of these “samples” to your image. Then when you are adjusting the image using any of the choices under the Image > Adjustments menu, the Info palette readouts will change into two readouts for each Color Sampler (Figure 1.40). The left number indicates what the color was before the adjustment; the right number indicates what the color will be after the adjustment. You can even add a color sample to your image while an adjustment dialog box is active by holding the Shift key and clicking on the image. (The Color Sampler tool does not need to be active to do this.)
Figure 1.39. Color samples and Info palette readouts. (©2005 Stockbyte, www.stockbyte.com)
To remove a sample, hold the Option key (Mac) or Alt key (Windows), and click on the sample, or just drag it off the screen. Or, if you'd like to remove all the color samples, click the Clear button in the options bar. (It's available only when the Color Sampler tool is active.) Occasionally you may want to hide the sample points when you're working on your image; you can do this by choosing Color Samples from the side menu of the Info palette. We'll use these samples when you read about color correction in Chapter 8, “Color Correction.”
 | Photoshop CS2's Info Palette can display extra information that is usually only found in the Status area that appears at the bottom edge of each document. To control which status readouts are visible, choose Palette Options from the side menu of the Info palette. |