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Resolution is a measure of how finely a device displays graphics with pixels. It is used by printers, scanners, monitors (TV, computer), mobile devices and cameras. There are two types/ways of measuring resolution:

  1. The amount of (dpi) dots per inch. Printers and scanners work with higher resolutions than computer monitors. Current desktop printers can support 300dpi +, flatbed scanners from 100-3600dpi+. In comparison computer monitors support 72-130 dpi. This is also known as 'Image resolution'.
  1. The size of the frame (as in video) and monitor. For example the size of video frame used for British Televisions is 768x576, whereas American TVs use 640x480.

PPI (Pixels Per Inch) is a term also used to define the resolution for bitmaps.

"Knowing the pixel dimensions, you know how much detail is contained in the image; the number of dots per inch on the output device tells you how big that same image will be, and how easy it will be to see the individual pixels." (Chapman and Chapman, Digital Multimedia, 2004)

Monitor resolution is sometimes quoted in dots per inch, because of the tendency in computer systems to keep this value fixed and to increase the pixel dimensions of the displayed image when a larger display is used.

When you view a bitmap of 100x80 pixels on a 96 dpi monitor, its physical size will be smaller than on a 72 dpi monitor. Likewise if you change the monitor resolution from 1024x768 to 1280x1024 the bitmap will look smaller.

"If an image's resolution is lower than that of the device on which it is to be displayed, it must be scaled up, a process which will require the interpolation of pixels. This can never be done without loss of image quality, so you should try to ensure that any images in your multimedia productions have an image resolution at least as high as that of the monitors on which you expect your work to be viewed." (Chapman & Chapman, Digital Multimedia, 2004)

The opposite is true of this. Interestingly if an image scanned at 72 dpi is viewed on a 72 dpi monitor, the quality won't be as good as an image scanned at 300 dpi being viewed at 72 dpi. The problem with the higher resolution image is that it will have a larger file size and take longer to download over a network.

Next: Bitmap Resolution