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DocuColor 8000/7000 Operator Manual
9-5
9. Hints and tips
What is the difference between ppi and dpi?
The term ppi (pixels per inch) originated in the world of computers,
and dpi (dots per inch) in the world or printing, but today they are
often used interchangeably.
What resolution should I use to scan an image?
As with taking a digital photo, your intended use for the image
determines your best scanning resolution. For example, a 4x6
inch photograph scanned at 300 ppi will have large pixel
dimensions and will appear large on a computer screen, while the
same photograph scanned at 72 ppi will have fewer pixels and will
appear much smaller on a screen.
Scanning resolution is expressed in terms of dpi or ppi. The
scanning resolution not only determines how many pixels will be
captured, it also gets embedded into the image as an invisible
piece of information for future output devices. To calculate the
pixel dimensions of a scanned photograph, multiply the scanning
resolution by the dimension in inches: Resolution x Inches =
Pixels. Using this formula you can calculate the pixel dimensions,
for example, of a 4x6 inch photograph scanned in using 300 ppi:
• 300 pixels/inch x 4 inches = 1200 pixels
• 300 pixels/inch x 6 inches = 1800 pixels
This means that your 4" x 6" photograph will be displayed as 1200
x 1800 pixels on your monitor, making it look very large on your
monitor and causing the image to spill over the edges.
You could resize the scanned photograph in your main imaging
application (such as Adobe Photoshop or Paint Shop Pro), or you
could rescan it using a lower resolution (ppi) setting. To calculate
the resolution that you should use to scan a photo/image, first
decide how big you want your image to appear on your monitor
(Pixels/Inches = Resolution).
For example, if you want your 4" by 6" photograph to appear as
400 x 600 pixels on the monitor, then you would scan it in at 100
ppi. If you want to create a 100 x 150 pixel thumbnail, you would
scan in your 4 inch x 6 inch photograph at 25 ppi.