General information about scanning resolution in Publisher

Scanned images can drastically increase the amount of time and disk space it takes to save a file, as well as the amount of time it takes to print. The amount of detail recorded by the scanner is measured in dots-per-inch (dpi). The higher the resolution or dpi, the more detail in the image and the larger the file size. When you add a scanned image to a file, you may want to keep the following points in mind:

• Use the optimum scanning resolution to keep images from getting unnecessarily large. Do this by matching the scanning resolution to the capacity of the output device.
• If an image has more resolution than a printer can print, the printer simply ignores the excess.
• The best scanning resolution is equal to two times the number of lines per inch (lpi) of the printer.

The following table will help you select the optimum scanning resolution.

Output device	Output dpi	Output lpi	Scanning dpi
Monitor	96	NA	96
Laser printer	300	55-65	120
Laser printer	600	65-85	150
Ink-jet printer	300	50-60	110
Dye sub printer	300	55-70	125
Imagesetter	1250+	120-150	300

You may also want to consider the following "rules of thumb."

Scan at an Appropriate Resolution

If you are scanning in color or grayscale, scan at no more than one-half the resolution of your printer. Therefore, if your laser printer prints at 600 dpi, scan at no more than 300 dpi. If you are scanning in black and white, scan at no more than your printer resolution, but make sure that your scanner is set to "black and white" or "line art."

Scan at an Appropriate Color Depth

If your original artwork is in color, but you will only be printing to a black and white printer, scan it in grayscale. If your original artwork is a black and white line diagram, scan it in black and white.

Scan at an Appropriate Size

Use your scanning program to scale the original artwork. For example, if you are scanning a 5-by-5-inch logo to place on a business card, use the scaling controls in your scanner software to reduce it to around 20-percent (1-by-1-inch). Then use the scaling commands in Publisher to get the logo exactly the right size.

When you import a scanned image into a file, what you are bringing in is a rectangular grid of dots of different colors. If you scan an entire letter-sized sheet of paper at 300 dots per inch, that rectangular grid contains about 8,415,000 individual dots.