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5-6. Resolution

Resolution is a measure of the finest details that can be detected in an image.  In digital imaging, resolution is measured in the number of pixels, in both height and width that make up an image.  The higher the resolution of an image, the greater its clarity and definition.  However, disk storage space, memory and data processing time requirements increase as resolution increases.   Therefore, you must guard against "over-scan," the use of unnecessarily high resolution.  For example—If the image is only to be displayed on a monitor, then pixels per inch is the most important factor.  The maximum resolution for most computer screens is 72 dpi.  It makes no sense to scan at resolutions of 500 DPI if the image will only be shown on a computer screen.

For electronic image editing and processing, monitors used to view images may be set at a higher than normal resolution.  Higher resolutions allow you to view a sharper looking image but they make the image appear smaller on the screen.  Monitor resolution does not affect final image output, but higher than normal screen settings can make image editing easier.

Output resolution is the number of dots per inch, dpi, used to display a digital image on a monitor or in print.  It is determined by the settings of the final output device (at DINFOS, 300 pixels/dpi per inch) and a mathematical formula. 

You can use the following formula to estimate input scan resolution for halftone printing, the type of printing done by most military news publications:

Magnification x Output device resolution / 2 = input scan resolution setting

  • Newspaper example.  You want your image to be an 8x10 photo in a newspaper.  The printed newspaper page (output device) has a 300 dpi resolution requirement.
10 (largest photo dimension) x 300 (output dpi) /2 = 1500 dpi input scanning resolution.  (You will adjust the scanner input setting to 1500)
You must set your scanning device to capture the image at 1500 dpi to ensure optimal quality on the printed page.
  • Online publication example.  If your end product is an 8x10 digital image for a web page, and will not also be used in a newspaper, only a lower-resolution product, 72 ppi/dpi scanner output, will be required.  The equation would look like this: 10 x 72 /2 = 360 ppi/dpi (input resolution setting is 360 ppi/dpi)

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