INTRODUCTION TO PHOTOSHOP 4.0 (Continued)

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SCANNING BASICS

Each scanner has its own software that controls how it works. This software is considered TWAIN Compliant (Technology Without An Independent Name). You can scan from this software, or from within Photoshop itself

Before scanning, you need to make choices that affect the quality and usefulness of the resulting file:
	Determine the scan resolution of the image, based on final output.
	Define the area to be scanned, and scan a bit larger than the actual size you want.
	Determine the optimal dynamic range (if your scanner lets you set black points and white points). (Refer to Basic Image Correction for more information.)
	Check for color casts (imbalance in one or more colors) to be eliminated during the scan.

While scanning, pay attention to the following details:
	Ensure the scanner glass is clean, and that the quality of the source image is the best possible.
	Position the source document squarely on the scanner, as repairing misalignment or rotating an image after the scan can degrade image quality.
	Scan at the appropriate resolution, depending on the intended use of the resulting image (Print or Electronic Publication).
	Don't use the scanner's interpolated resolution; use only the scanner's true optical resolution, or use Photoshop's built-in resolution tools.
	For better results with color photos, scan in 24-bit RGB color mode, then if needed, convert to another format (i.e., 256 color) from within Photoshop.
	Take a preview scan and select only the portion (plus a bit) of the image you want in the final scan.

Recommended Scanning Resolutions of several common printers & printing services:

Output	Optimal Scan Resolution (DPI)
Printer / Service Type	Line Art	Grayscale / Continuous Tone
LaserJet 5M (600dpi, laser)	600dpi	150-200dpi
Epson Stylus Color (720dpi, inkjet) (based on 1.5 - 2 times screen frequency of 120 lpi)	720dpi	180-240dpi
HP DeskWriter 680C (600dpi B&W, 300dpi color, inkjet)	600dpi	100-150dpi
Fuji & Dye-sublimation printers (200-300dpi)	N/A	200dpi for images; 300dpi for text
Web Page (72-96dpi)(200-300dpi)	72 or 96dpi	72 or 96dpi
Newspaper(72-96dpi)(200-300dpi)		125-225dpi
Magazine		200-265dpi
Art Books		225-300dpi

Other Scanning Recommendations for various types of Source Documents:

Black and White Illustrations, and Pages for OCR	Use "Line Art" or "Black & White" Mode. Scan Line Art at the resolution of the output device.
Black & White Photos, Sketches, Drawings	Use "Grayscale" Option, 256 levels
Color Photographs	Use RGB Color, or 24-bit to 36-bit color setting.