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.Luminance=100 (white)black).Images produced using black-and-white orB.Green to red componentgrayscale scanners typically are displayed inC.Blue to yellow componentD.Luminance=0 (black) Grayscale mode. ADOBE PHOTOSHOP 6.0 113User GuideAlthough Grayscale is a standard color Indexed Color modemodel, the exact range of grays represented canThis mode uses at most 256 colors.Whenvary, depending on the printing conditions.converting to indexed color, Photoshop builds aIn Photoshop, Grayscale mode uses the rangecolor lookup table (CLUT), which stores anddefined by the working space setting that you haveindexes the colors in the image.If a color in thespecified in the Color Settings dialog box.original image does not appear in the table,(See About working spaces on page 125.)the program chooses the closest one or simulatesthe color using available colors.These guidelines apply to converting images toand from Grayscale mode:By limiting the palette of colors, indexed color canreduce file size while maintaining visual quality" You can convert both Bitmap-mode and colorfor example, for a multimedia animation appli-images to grayscale.cation or a Web page.Limited editing is available" To convert a color image to a high-qualityin this mode.For extensive editing you shouldgrayscale image, Photoshop discards all colorconvert temporarily to RGB mode.(Seeinformation in the original image.The gray levels Converting to indexed color (Photoshop) on(shades) of the converted pixels represent thepage 118.)luminosity of the original pixels.You can mix information from the colorMultichannel modechannels to create a custom grayscale channelThis mode uses 256 levels of gray in each channel.by using the Channel Mixer command.Multichannel images are useful for specialized" When converting from grayscale to RGB, theprinting for example, converting a duotone forcolor values for a pixel are based on its previousprinting in Scitex CT format.gray value.A grayscale image can also be convertedThese guidelines apply to converting images toto a CMYK image (for creating process-colorMultichannel mode:quadtones without converting to Duotone mode)or to a Lab color image." Channels in the original image become spotcolor channels in the converted image.Duotone mode" When you convert a color image to multi-channel, the new grayscale information is based onThis mode creates duotone (two-color), tritonethe color values of the pixels in each channel.(three-color), and quadtone (four-color) grayscaleimages using two to four custom inks." Converting a CMYK image to multichannel(See Printing duotones on page 384.)creates cyan, magenta, yellow, and black spotchannels. CHAPTER 3114Working with Color" Converting an RGB image to multichannel For more information, see Identifyingcreates cyan, magenta, and yellow spot channels.out-of-gamut colors (Photoshop) inonline Help." Deleting a channel from an RGB, CMYK,or Lab image automatically converts the image toMultichannel mode.(See About color channels Aon page 116 for more information on channels.)B" To export a multichannel image, save it inPhotoshop DCS 2.0 format.CColor gamuts (Photoshop)A gamut is the range of colors that a color systemcan display or print.The spectrum of colors seenA.Lab color gamut B.RGB color gamutC.CMYK color gamutby the human eye is wider than the gamut availablein any color model.Among the color models used in Photoshop,Adjusting the monitor displayL*a*b has the largest gamut, encompassing allAlthough the RGB color model used by computercolors in the RGB and CMYK gamuts.Typically,monitors is capable of displaying much of thethe RGB gamut contains the subset of these colorsvisible spectrum, the video system sending data tothat can be viewed on a computer or televisiona given monitor often limits how many colors canmonitor (which emits red, green, and blue light).be displayed at once.By understanding how colorTherefore, some colors, such as pure cyan or puredata is measured in digital files and on-screen,yellow, can t be displayed accurately on a monitor.you can better adjust color display settings toThe CMYK gamut is smaller, consisting only ofoffset the limitations of your video system.colors that can be printed using process-colorFor more information, see Specifying 8-bitinks.When colors that cannot be printed arecolor display (Photoshop) in online Help.displayed on-screen, they are referred to as out-of-gamut colors that is, outside the CMYK gamut. ADOBE PHOTOSHOP 6.0 115User GuideMaking previews display more quickly RGB color display can also vary betweenPhotoshop and ImageReady.In Photoshop,(Photoshop)you can select from several RGB color spaces whenThe Use Pixel Doubling preference option speedsediting images.As a result, images created inup the preview of a tool or command s effects byPhotoshop may use an RGB color space that differstemporarily doubling the size of the pixelsfrom the monitor RGB color space used by(halving the resolution) in the preview.ThisImageReady.You can adjust the RGB coloroption has no effect on the pixels in the file;display during image preview to compensate forit simply provides faster previews with the toolsdifferences between Photoshop and ImageReady.and commands.To adjust RGB color display for cross-platformTo speed up previews:variations (ImageReady):1 Choose Edit > Preferences > Display & Cursors.Choose View > Preview and choose an option for2 Select Use Pixel Doubling, and click OK.adjusting the color display:" Uncompensated Color (the default option) toAdjusting color display for cross-platformview the image with no color adjustment.variations" Standard Macintosh Color (Windows) to viewRGB color display on a computer monitorthe image with color adjusted to simulate avaries with the operating system used by thestandard Macintosh monitor.computer.For example, an image appears" Standard Windows Color (Mac OS) to view thedarker on a Windows system than on a Mac OSimage with color adjusted to simulate a standardcomputer (because the standard RGB colorWindows monitor.space is darker in Windows than in Mac OS).The Preview commands in ImageReady enable Note: These options adjust color display only.you to compensate for cross-platform differences No changes are made to pixels in the image.in RGB color display during image preview.In Photoshop, you can simulate cross-platformdifferences by using the Macintosh RGB, WindowsRGB, and Monitor RGB commands in the View >Proof Setup menu
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