Every file has a color mode, also called an image mode or just plain mode. To determine the color mode of an image, look in the title bar of the image window or choose Image➪Mode. Color modes define the color values used to display the image. Photoshop offers eight different modes and allows you to convert images from one mode to another. The color mode you choose for a particular image depends on a couple of factors:
-->The file format you plan to save it in. Some modes call for specific file formats. You may find that a certain format is unavailable because your file isn’t in the appropriate color mode.
-->The end use for the image. Do you plan to post the image on the Web? Or are you putting it in a brochure that will be offset printed?
The next few sections provide a brief description of each mode and any file format or usage connections. For examples of some modes, in full, living color, be sure to check out Color Plate 2-2.
RGB Color
Uses: RGB is the gold standard for most scanners, all monitors, and some desktop inkjet printers. And it’s the primary color mode (with Indexed Color being secondary) to use with any images to be viewed on-screen (whether on the Web or in any kind of multimedia presentation).
File formats: RGB can handle just about every format except GIF.
RGB can be considered the default color mode of Photoshop. RGB images contain values of 0–255 for each of three colors — red, green, and blue. With 8 bits of color information for each of the three colors, these 24-bit images can reproduce up to 16.7 million colors on-screen. And 48-bit images (16 bits per color) can display even more. Most scanners also scan images in RGB, all monitors display in RGB, and some desktop inkjet printers prefer to print RGB (rather than CMYK) images. Remember that the RGB mode in Photoshop varies according to the RGB Working Space setting you have selected in the Color Settings dialog box.
CMYK Color
Uses: CMYK is the standard for images that are color separated for offset printing.
File formats: CMYK can handle just about every format except GIF.
CMYK images contain a percentage of one or more of four-process color inks — cyan, magenta, yellow, and black. Darker colors have higher percentages, whereas lighter colors have lower percentages. Pure white is created when all four colors have a value of 0%. Many other composite printing devices also require images to be in CMYK mode. Again, like RGB mode, remember that the CMYK mode in Photoshop can vary according to the CMYK Working Space setting you have selected in the Color Settings dialog box.
Make sure that you do all of your image editing in RGB mode, where you have access to the full range of filters. When you complete your editing, convert the image from RGB to CMYK.
Grayscale
Uses: Grayscale mode is for black-and-white (and all shades of gray in between) images.
File formats: All of the most commonly used file formats accept Grayscale mode.
Grayscale images contain up to 256 levels of gray. Each pixel has a brightness value ranging from 0 (black) to 255 (white). You can scan an image in Grayscale mode, or you can convert color images to grayscale. If you convert a color image to grayscale, Photoshop discards all the color information, and the remaining gray levels represent the luminosity of the pixels.
You can also convert a grayscale image to a color image, which, while it doesn’t convert your grayscale image to color, it allows you to apply color on top of the grayscale image.
Monotone, Duotone, Tritone, and Quadtone
Uses: Because printing presses can print only about 50 gray levels per ink color, duotones, which use two to four inks, are used to increase the range of tones of grayscale images. Duotones are often created by using black and spot colors (premixed inks), although you can also use process colors.
File formats: The only file formats that can save duotones, tritones, and quadtones are native Photoshop, Photoshop 2.0, EPS, PDF, Large Document Format, or Photoshop Raw. These modes create one-color, (monotone), two-color (duotone), three-color (tritone), and four-color (quadtone) images. Note that Photoshop lumps all the various “tone” modes under duotone. You will find a pop-up menu in the Duotone options dialog box where you can select the various options. Unlike RGB and CMYK images where the components of the image display with different colors, the monotones, duotones, tritones, and quadtones have the colors mixed throughout the image. The colored inks are used to reproduce tinted grays, not the different colors you find in RGB and CMYK images.
To access the Duotone mode, you must first convert the color image to grayscale by choosing Image➪Mode➪Grayscale. Then choose Image➪Mode➪Duotone. In the dialog box that appears, choose Monotone, Duotone, Tritone, or Quadtone from the pop-up menu. Next, select ink colors — either spot or process — by clicking the swatches. Finally, you can adjust the curves settings and tell Photoshop how to distribute the ink(s) among the various tones.
Note that you do not have access to the individual color channels in Duotone mode. The only manipulation that you do is with the curves settings. If you are new to these modes, you need to know that Photoshop offers numerous preset duotones, tritones, and quadtones. To access these presets, click the Load button and go to the Duotones folder (which is located in the Presets folder in the Photoshop folder).
Indexed Color
Uses: Indexed Color mode is primarily for Web graphics and multimedia displays.
File formats: Indexed Color mode supports a variety of formats, with GIF being the most popular.
Others formats supported include Photoshop, Photoshop 2.0, Photoshop Raw, BMP, EPS, ElectricImage, Large Document Format, PCX, PDF, PICT, PICT Resource, PNG, Targa, and TIFF. Indexed Color mode uses 256 colors or less; what graphics aficionados call 8-bit color. When you convert an image to indexed color, Photoshop builds a Color Lookup Table (CLUT), which stores and indexes the color. (Note the Color Table option in the Mode menu.) If a color in the original image isn’t in the table, Photoshop chooses the closest match or makes a new one from the available colors. The small amount of colors reduces the file size, which is why the GIF file format, the preferred format for Web graphics, uses this mode. The Indexed Color mode does not support layers, and editing capabilities are limited.
Lab Color
Uses: Lab Color mode provides a consistent color display, which is ideal for high-end retouching of images.
File formats: You can save an image in Lab Color mode in native Photoshop, Photoshop Raw, EPS, TIFF, PDF, JPEG 2000, Large Document Format, or Photoshop DCS 1.0 and 2.0 formats. You can save images containing 48 bits (16 bits per channel) in Photoshop, Photoshop Raw, Large Document Format, and TIFF formats.
Lab Color mode is usually thought of as the internal color mode Photoshop uses when converting from one color mode to another — for example, when going from RGB to CMYK. It is also the mode preferred by color-retouching experts because it is considered to be device independent (it appears consistent on various devices). Lab Color mode consists of a lightness channel and two additional channels, a and b, which contain the range of color from green to red (a) and blue to yellow (b).
Bitmap
Uses: This mode is best for scanned line art and signatures (your John Hancock).
File formats: Photoshop, Photoshop 2.0, EPS, TIFF, PDF, BMP, PNG, GIF, PNG, PCX, PICT, PICT Resource, Portable Bitmap, and Wireless Bitmap. Bitmap images contain pixels that are either black or white, exclusively. You must convert color images to grayscale before you can access Bitmap mode. Upon choosing Image➪Mode➪Bitmap, a dialog box appears, offering options for resolution and method. The various methods give different appearances so try each one to see which you prefer.
If you save a file in Bitmap mode as an EPS you can convert the white areas in the image to transparent areas. This allows you to overlay the file over a background containing color or an image, and only the dark pixels show.
Multichannel
Uses: Multichannel mode is for special printing needs or as an intermediate mode when converting between different color modes.
File formats: The only file formats available for multichannel images are native Photoshop, Photoshop 2.0, Photoshop DCS 2.0, Large Document Format, or Photoshop Raw formats. The Multichannel mode comprises multiple grayscale channels, each containing 256 levels of gray. Whenever you delete or mix channels, you end up with a multichannel image. You can also convert any image with more than one channel to this mode. In a multichannel image, each channel becomes a spot channel, with 256 levels of gray.
-->The file format you plan to save it in. Some modes call for specific file formats. You may find that a certain format is unavailable because your file isn’t in the appropriate color mode.
-->The end use for the image. Do you plan to post the image on the Web? Or are you putting it in a brochure that will be offset printed?
The next few sections provide a brief description of each mode and any file format or usage connections. For examples of some modes, in full, living color, be sure to check out Color Plate 2-2.
Color modes affect the number of colors that are displayed, as well as the size of the file and the number of channels. Each mode is also represented by one or more channels, where the color data is stored. Grayscale images have one channel — black. CMYK images have four channels — cyan, magenta, yellow, and black.
RGB Color
Uses: RGB is the gold standard for most scanners, all monitors, and some desktop inkjet printers. And it’s the primary color mode (with Indexed Color being secondary) to use with any images to be viewed on-screen (whether on the Web or in any kind of multimedia presentation).
File formats: RGB can handle just about every format except GIF.
RGB can be considered the default color mode of Photoshop. RGB images contain values of 0–255 for each of three colors — red, green, and blue. With 8 bits of color information for each of the three colors, these 24-bit images can reproduce up to 16.7 million colors on-screen. And 48-bit images (16 bits per color) can display even more. Most scanners also scan images in RGB, all monitors display in RGB, and some desktop inkjet printers prefer to print RGB (rather than CMYK) images. Remember that the RGB mode in Photoshop varies according to the RGB Working Space setting you have selected in the Color Settings dialog box.
CMYK Color
Uses: CMYK is the standard for images that are color separated for offset printing.
File formats: CMYK can handle just about every format except GIF.
CMYK images contain a percentage of one or more of four-process color inks — cyan, magenta, yellow, and black. Darker colors have higher percentages, whereas lighter colors have lower percentages. Pure white is created when all four colors have a value of 0%. Many other composite printing devices also require images to be in CMYK mode. Again, like RGB mode, remember that the CMYK mode in Photoshop can vary according to the CMYK Working Space setting you have selected in the Color Settings dialog box.
Make sure that you do all of your image editing in RGB mode, where you have access to the full range of filters. When you complete your editing, convert the image from RGB to CMYK.
Grayscale
Uses: Grayscale mode is for black-and-white (and all shades of gray in between) images.
File formats: All of the most commonly used file formats accept Grayscale mode.
Grayscale images contain up to 256 levels of gray. Each pixel has a brightness value ranging from 0 (black) to 255 (white). You can scan an image in Grayscale mode, or you can convert color images to grayscale. If you convert a color image to grayscale, Photoshop discards all the color information, and the remaining gray levels represent the luminosity of the pixels.
You can also convert a grayscale image to a color image, which, while it doesn’t convert your grayscale image to color, it allows you to apply color on top of the grayscale image.
Monotone, Duotone, Tritone, and Quadtone
Uses: Because printing presses can print only about 50 gray levels per ink color, duotones, which use two to four inks, are used to increase the range of tones of grayscale images. Duotones are often created by using black and spot colors (premixed inks), although you can also use process colors.
File formats: The only file formats that can save duotones, tritones, and quadtones are native Photoshop, Photoshop 2.0, EPS, PDF, Large Document Format, or Photoshop Raw. These modes create one-color, (monotone), two-color (duotone), three-color (tritone), and four-color (quadtone) images. Note that Photoshop lumps all the various “tone” modes under duotone. You will find a pop-up menu in the Duotone options dialog box where you can select the various options. Unlike RGB and CMYK images where the components of the image display with different colors, the monotones, duotones, tritones, and quadtones have the colors mixed throughout the image. The colored inks are used to reproduce tinted grays, not the different colors you find in RGB and CMYK images.
To access the Duotone mode, you must first convert the color image to grayscale by choosing Image➪Mode➪Grayscale. Then choose Image➪Mode➪Duotone. In the dialog box that appears, choose Monotone, Duotone, Tritone, or Quadtone from the pop-up menu. Next, select ink colors — either spot or process — by clicking the swatches. Finally, you can adjust the curves settings and tell Photoshop how to distribute the ink(s) among the various tones.
Note that you do not have access to the individual color channels in Duotone mode. The only manipulation that you do is with the curves settings. If you are new to these modes, you need to know that Photoshop offers numerous preset duotones, tritones, and quadtones. To access these presets, click the Load button and go to the Duotones folder (which is located in the Presets folder in the Photoshop folder).
Indexed Color
Uses: Indexed Color mode is primarily for Web graphics and multimedia displays.
File formats: Indexed Color mode supports a variety of formats, with GIF being the most popular.
Others formats supported include Photoshop, Photoshop 2.0, Photoshop Raw, BMP, EPS, ElectricImage, Large Document Format, PCX, PDF, PICT, PICT Resource, PNG, Targa, and TIFF. Indexed Color mode uses 256 colors or less; what graphics aficionados call 8-bit color. When you convert an image to indexed color, Photoshop builds a Color Lookup Table (CLUT), which stores and indexes the color. (Note the Color Table option in the Mode menu.) If a color in the original image isn’t in the table, Photoshop chooses the closest match or makes a new one from the available colors. The small amount of colors reduces the file size, which is why the GIF file format, the preferred format for Web graphics, uses this mode. The Indexed Color mode does not support layers, and editing capabilities are limited.
Lab Color
Uses: Lab Color mode provides a consistent color display, which is ideal for high-end retouching of images.
File formats: You can save an image in Lab Color mode in native Photoshop, Photoshop Raw, EPS, TIFF, PDF, JPEG 2000, Large Document Format, or Photoshop DCS 1.0 and 2.0 formats. You can save images containing 48 bits (16 bits per channel) in Photoshop, Photoshop Raw, Large Document Format, and TIFF formats.
Lab Color mode is usually thought of as the internal color mode Photoshop uses when converting from one color mode to another — for example, when going from RGB to CMYK. It is also the mode preferred by color-retouching experts because it is considered to be device independent (it appears consistent on various devices). Lab Color mode consists of a lightness channel and two additional channels, a and b, which contain the range of color from green to red (a) and blue to yellow (b).
Bitmap
Uses: This mode is best for scanned line art and signatures (your John Hancock).
File formats: Photoshop, Photoshop 2.0, EPS, TIFF, PDF, BMP, PNG, GIF, PNG, PCX, PICT, PICT Resource, Portable Bitmap, and Wireless Bitmap. Bitmap images contain pixels that are either black or white, exclusively. You must convert color images to grayscale before you can access Bitmap mode. Upon choosing Image➪Mode➪Bitmap, a dialog box appears, offering options for resolution and method. The various methods give different appearances so try each one to see which you prefer.
If you save a file in Bitmap mode as an EPS you can convert the white areas in the image to transparent areas. This allows you to overlay the file over a background containing color or an image, and only the dark pixels show.
Multichannel
Uses: Multichannel mode is for special printing needs or as an intermediate mode when converting between different color modes.
File formats: The only file formats available for multichannel images are native Photoshop, Photoshop 2.0, Photoshop DCS 2.0, Large Document Format, or Photoshop Raw formats. The Multichannel mode comprises multiple grayscale channels, each containing 256 levels of gray. Whenever you delete or mix channels, you end up with a multichannel image. You can also convert any image with more than one channel to this mode. In a multichannel image, each channel becomes a spot channel, with 256 levels of gray.
Selecting a Color Mode in Photoshop
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