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PhotoShop Image Modes
This information supports concepts presented in the book Adobe PhotoShop 5.5 Classroom in a Book, published by Adobe Press, 1999, page 414.
PhotoShop has several different image types/modes you can work with. Using the correct mode can minimize your file size & processing time, and is essential for obtaining quality output.
To select the different PhotoShop modes: Image Menu—Mode and hold down the mouse button.
Grayscale Modes
Bitmap: 1 1-bit channel = 2 available shades: black and white.
Grayscale: 1 8-bit channel = 256 brightness levels, ranging from 1 (black) to 255 (white).
Duotone: 1 8-bit channel = 256 brightness levels like Grayscale, but can use 2, 3, or 4 inks during printing, more variety of grays than grayscale
Color Modes
Indexed Color: 1 8-bit channel. Each pixel can be assigned a color = 256 colors
RGB Color: 3 8-bit channels = (3 X 8 channels = 24-bits), 2 pixel depth to the 24th power = 16.7 millions possible colors.
CMYK Color: 4 8-bit channels = (4 X 8 channels = 32-bits), 2 pixel depth to the 32nd power = 4 billion possible colors.
The following table summarizes resolution values for several printing conditions:
This information supports concepts presented in the book Adobe PhotoShop 5.5 Classroom in a Book, published by Adobe Press, 1999, page 432.
|
Type |
Measurement |
Laser Printer |
Newspaper |
Magazine |
|
Image Resolution |
pixels/inch (ppi) |
110-170 ppi |
13-200 ppi |
200-300 ppi |
|
Halftone Screen |
Lines/inch (lpi) |
71, 85 lpi typical |
85, 100 lpi typical |
133, 150 lpi typical |
|
Printer Resolution |
Dots/inch (dpi) |
600 dpi typical |
1270, 2540 dpi typical |
1270, 2540 dpi typical |
