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Color à la Mode

Now let's take a look at color as it applies to creating a new file in Photoshop (by choosing File, New or pressing Ctrl+N). One of the options found in the dialog box is Mode, which refers to the color mode of your file. The color mode you decide upon determines the specific method (called a color model) that Photoshop uses to color the pixels in your image.

What Is a Pixel?

A pixel is a picture element in an image. It's a lot like those pegs you used to place in your Lite-Bright toy, except you're given a lot more pixels to play with in a high-quality image. But unlike Lite-Bright, you can't lose pixels under the sofa.

The color mode choices are

  • RGB Color—(Red, Green, Blue) This is the color space (an arrangement and limitation of the colors that can be expressed in an image file) that your monitor uses to display your image. Using this mode gives you the most accurate screen representation of your image's colors. Always try to use this mode for color work.

  • Grayscale—This mode has a color space that is limited to 256 percentages of black. Medium gray, for example, is 50% black (or 128 on the brightness scale in grayscale images). Photoshop performs operations more quickly in Grayscale mode because there is only one channel (black), and therefore it requires 1/3 the channel information needed with an RGB image.

  • CMYK Color—This acronym refers to cyan, magenta, yellow, and black, the colors used in printing. Photoshop performs operations slower in CMYK mode because there are four channels to calculate. Considering that the CMYK color space is smaller than that of RGB, it is highly recommended that you don't create new files in this mode.

  • Lab Color—This is the largest color space there is (larger than RGB), but that's still not a good reason to create files in this mode. Because the color space is the largest, other modes can pass through it without losing any color information. For this reason, it is a good mode to use when making mode transitions.

  • Bitmap—This mode (also referred to as one-bit mode) is perfect if you want to create line art files in black and white. This mode doesn't make shades of gray as does the Grayscale mode—it just uses black and white. Because Bitmap mode only relies on two colors, files tend to be very small.

The only two modes that are easy and intuitive enough for the Photoshop novice to work with are the RGB and Grayscale modes. Avoid using any other modes for a new file until you feel more at home with the application. There's a practical reason for this advice; you have access to more of Photoshop's features in these modes.

Keep an Eye Out When Creating a New File

When you create a new image file, Photoshop remembers all the settings in the New dialog box from the last time you created a new file. If you create a grayscale image, the mode of every new file you create after that is set to Grayscale until you change the mode in the New file dialog box.

Changing Modes

Before moving into the area of choosing colors for your image, let's discuss the need to change modes after you've already been working with a file. Sometimes you might create a file with one goal in mind (a piece of full color art, for example), and then you decide you want to use the art somewhere else, ("Hey, this would make a great illustration on my Web banner—I'll need to convert this to a GIF file.")

If you're just starting out in Photoshop, or even if you've been working with it for a while, you shouldn't need to switch color modes very often (if you are doing a lot of mode switching, you need to ask yourself why). When you do decide to change color modes, you should first save a copy of your file and be absolutely sure about the mode you want to use. Don't convert your file from RGB to CMYK and back to RGB again; jumping back and forth between modes can wreck the color in your file because different Photoshop modes have different color spaces.

Here are the only reasons you really need to switch color modes:

  • To change a Photo CD file to RGB color from Lab color—See the section on opening Photo CD images in Chapter 4, "Opening and Saving Grace," for more information.

  • To convert your RGB file to CMYK—If you need to create a file that's destined for a commercial printer, work in RGB and then convert the file. This creates a file that's 1/4 larger than its RGB cousin. (I spoke with several large printers who all agreed that delivering RGB files is the best way for new folks to go.)

  • To switch color images to Indexed Color—You don't paint or create in Indexed Color mode, but instead convert an RGB copy of your work to Indexed Color. To convert a file to Indexed Color (to prepare an image for saving as a GIF file, let's say), choose Image, Mode, Indexed Color (see Figure 3.2), and then choose Adaptive as your palette (don't use Web, even though it sounds tempting; see Figure 3.2). Then enter 256 in Colors, pick Diffusion for the Dither setting, and for Color Matching click the Best button. When you use these settings, your Indexed Color images look great on any system.

  • To convert color images to grayscale—You can do so directly by going to Image, Mode, Grayscale, but the conversion isn't a truly accurate one. You lose all color information in the process, and the grayscale image might also end up a bit darker than the original. Instead, open the color file you want to convert. Choose Image, Mode, Lab Color. Click the Channels palette to activate it (if it isn't visible, choose Window, Show Channels or press F7), and then click the Lightness channel (no, it's not a cable station, as you see in Figure 3.3). Now choose Image, Mode, Grayscale and you see a box asking if you want to discard the other channels. Yes! Press OK, Ansel Adams.

CMYK: The Printing Mode

As touched upon in Chapter 2, "What's Your Preference, Sonny?," our advice is to use RGB color and avoid CMYK mode. Why? Because CMYK is designed to create the color separations that are used for color printing (and this is full-blown commercial printing, not an inkjet or LaserJet printer). It was not designed as a display mode. If you use it, you're asking an RGB monitor to display inks as they will print, and therein lies the trouble. Monitors, even the best-calibrated ones, show duller images.

There's no good reason for you to convert your files for printing separations. As a matter of fact, many printers would rather you submit RGB files, particularly those using ICC Profiles, because they've already calibrated their equipment and they don't want your CMYK profile messing up their settings.

More Info About Indexed Color

An image that uses Indexed Color contains a maximum of 256 specific colors. Image formats such as GIF rely on Indexed Color as part of their coding. You can actually save TIFF or PSD files using Indexed Color, but the only advantage is a smaller document size. You lose most of the editing options in Photoshop, such as layers and soft-tip brushes, as well as most of the colors that make up your original image. It isn't worth the tradeoff. There are better options for reducing the saved size of your image.

Figure 3.2 The left side of the image is converted to Indexed Color mode using an Adaptive palette. The right side uses the Web palette. Even in grayscale, you can see how the image is affected.

Figure 3.3 Every image in this book was converted from RGB to Lab color to Grayscale.

Additional Ideas for Color Manipulating Mode

Before moving into the area of color, let's talk a little more about the Grayscale mode. Grayscale is not the same as Indexed Color mode, although both file types can contain only 256 unique values. Grayscale, as the egghead programmers will tell you, is a "special instance" of a color model. And whereas a grayscale image can be used with Photoshop's soft-tip brushes and several other full-featured commands, an Indexed color image, containing 256 color slots, cannot.

You can take advantage of the 256-value connection between Grayscale and Indexed color to create either tinted images, similar to sepia toning, or images with unusual color schemes. Here's how:

  1. Open (or create) a Grayscale image, and then choose Image, Adjust, Mode, Indexed Color.

  2. Choose Image, Mode, Color Table.

  3. Drag your cursor from the top color box to the bottom-right color box. The Color Picker appears with the legend "Select first color." Click any color you like. Click OK.

  4. Mr. Color Picker appears again, this time with the legend "Select last color." Make this an entirely different color from your first choice. Click OK, and then click OK in the Color Table dialog box. Poof! An instant psychedelic poster effect!

You can pick only a segment of the color table to change, or even click on a single Color Table box swatch to replace only one color. Additionally, you can choose different tables by checking out the Table drop-down list in the Color Table dialog box. My favorite is Spectrum, which severely messes with the color table of any RGB image that you've converted to Indexed color.

Stirring Things Up with the Channel Mixer

The Channel Mixer tool (see Figure 3.4) was incorporated in Photoshop 5.5 (you can access this filter from Image, Adjust, Channel Mixer). Channels are just another name for the color element information of each image; an RGB image has three channels, one for each color, whereas a grayscale image has just the black channel. Using an RGB image, you can get effects similar to placing colored filters on your camera just by adjusting the Color Mixer sliders. By clicking the Monochrome box, you flatten the color so it appears to be grayscale, but it's not. If you uncheck Monochrome again and adjust the R, G, or B sliders you get black and white with a colored tint. If you leave the Monochrome box checked, the effect is similar to placing colored filters on your camera with black-and-white film loaded; you shift the emphasis of the gray shading.

Figure 3.4 Click the Monochrome box to apply equal amounts of R, G, and B Info to the image, making a pseudo black-and-white image.

Find Ancient Treasure Using the Gradient Map

If you ever felt your image needed that "I just dropped acid" look then you need to know that you've been on the mind of someone at Adobe. By maneuvering to Image, Adjust, GradientMap, you open the Gradient Map editor (see Figure 3.5). The dialog box is deceiving, because it looks like there's nothing in there. That's because the wizard is hidden behind the curtains, Dorothy. Note the small box with the downward-pointing triangle. Click the box and you're given a long list of gradient presets you can use, or you can opt to load more if the zillion Adobe supplies aren't your cup of tea. Luckily, the dialog box isn't too big, so you can experiment to your heart's content to create your latest "posterized" masterpiece.

Figure 3.5 Whoa! Get out the lava lamp. Have your own '60s flashback using the Gradient Map editor.

The gradients are being applied to the Grayscale info of the image, making the effect similar to the one I suggested earlier using Color Tables.

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