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How do I decide which resolution to select when scanning?

Resolution refers to how many dots per inch (dpi) your image contains.

The best resolution for a scanned image depends on the type of image you're scanning and your final output device.

For most images except line art, use a scanning resolution that is approximately one third of your output resolution.

For example, use a scanning resolution up to 100 dpi with a 300 dpi laser printer, and up to 200 dpi with a 600 dpi laser printer.

For 1440 dpi ink jet printers, such as the EPSON Stylus Color or Photo series, use a scanning resolution of approximately 300 dpi.

For on-screen viewing, you can scan at 72 dpi.

Keep the following in mind when you choose a resolution:

  • Higher resolution settings result in larger file sizes.
    For example, an 8.5 x 11 inch original scanned at 300 dpi can produce a 24MB file.  The same original scanned at 72 dpi creates only a 1.3MB file.
  • Large files take longer to process and print, so consider the practical limitations of your computer system when selecting a resolution. To keep your file size manageable, select the lowest possible resolution that gives acceptable quality.
  • When scanning at a higher resolution, reduce the file size by scanning only part of the image.

 

R E S O L U T I O N
Resolution is the number of dots available to represent graphic detail in a given area:
on a computer screen the number of pixels per linear inch - ppi (72 to 96 ppi is the maximum a monitor displays)
on a printer the number of dots printed in a linear inch - dpi
on a scanner the number of pixels sampled per linear inch of the scanned image- ppi
IMAGE RESOLUTION is measured in pixels per inch - ppi
PRINTER RESOLUTION is measured in dots per inch - dpi
HALFTONE FREQUENCY
determines the size of printed dots		 is measured in lines per inch - lpi
If an image has a resolution of 72 ppi, this means it contains 5184 pixels in a square inch (72 pixels wide x 72 pixels high = 5184). Because the number of pixels in an image is fixed, when resolution decreases, the image size increases. Conversely, if we increase the resolution of an image, the image size (dimension) will decrease.
Higher resolutions allow for more detail and subtle color transitions in an image.
 
Scanning exercise
4x6 8x10
at
72 200 300 72 200 300
           
STUDY MATERIAL