Operation Manual

91
USING PHOTOSHOP
Color fundamentals
Last updated 12/5/2011
The Lab Color mode has a lightness component (L) that can range from 0 to 100. In the Adobe Color Picker and Color
panel, the a component (green-red axis) and the b component (blue-yellow axis) can range from +127 to –128.
Lab images can be saved in Photoshop, Photoshop EPS, Large Document Format (PSB), Photoshop PDF, Photoshop
Raw, TIFF, Photoshop DCS 1.0, or Photoshop DCS 2.0 formats. You can save 48-bit (16-bits-per-channel) Lab images
in Photoshop, Large Document Format (PSB), Photoshop PDF, Photoshop Raw, or TIFF formats.
Note: The DCS 1.0 and DCS 2.0 formats convert the file to CMYK when opened.
Grayscale mode
Grayscale mode uses different shades of gray in an image. In 8-bit images, there can be up to 256 shades of gray. Every
pixel of a grayscale image has a brightness value ranging from 0 (black) to 255 (white). In 16 and 32-bit images, the
number of shades in an image is much greater than in 8-bit images.
Grayscale values can also be measured as percentages of black ink coverage (0% is equal to white, 100% to black).
Grayscale mode uses the range defined by the working space setting that you specify in the
Color Settings
dialog box.
Bitmap mode
Bitmap mode uses one of two color values (black or white) to represent the pixels in an image. Images in Bitmap mode
are called bitmapped 1-bit images because they have a bit depth of 1.
Duotone mode
Duotone mode creates monotone, duotone (two-color), tritone (three-color), and quadtone (four-color) grayscale
images using one to four custom inks.
Indexed Color mode
Indexed Color mode produces 8-bit image files with up to 256 colors. When converting to indexed color, Photoshop
builds a color lookup table (CLUT), which stores and indexes the colors in the image. If a color in the original image
does not appear in the table, the program chooses the closest one or uses dithering to simulate the color using available
colors.
Although its palette of colors is limited, indexed color can reduce file size yet maintain the visual quality needed for
multimedia presentations, web pages, and the like. Limited editing is available in this mode. For extensive editing, you
should convert temporarily to RGB mode. Indexed color files can be saved in Photoshop, BMP, DICOM (Digital
Imaging and Communications in Medicine), GIF, Photoshop EPS, Large Document Format (PSB), PCX, Photoshop
PDF, Photoshop Raw, Photoshop 2.0, PICT, PNG, Targa®, or TIFF formats.
Multichannel mode
Multichannel mode images contain 256 levels of gray in each channel and are useful for specialized printing.
Multichannel mode images can be saved in Photoshop, Large Document Format (PSB), Photoshop 2.0, Photoshop
Raw, or Photoshop DCS 2.0 formats.
These guidelines apply when converting images to Multichannel mode:
Layers are unsupported and therefore flattened.