use two numbers to describe a printer抯 resolution, one for the vertical scanning and the other for horizontal. You can use both of these numbers to get a range of the dpi which can be used for high definition printing. For example, a printer with a resolution of 1200 x 600 will print a high definition image at 400 to 200 dpi. At 400 dpi, the image will be printed smaller and sharper. For many modern color printers, experts recommend 300 dpi as being a reasonable number (Milburn, 2000, p. 31).
The resolution of a file can be changed up or down by resizing the image. However, if the size of an image is increased or scaled up, the space between the original pixels must be filled in. The software used to make the file larger will fill in the space between the original pixels, however the result is often very fuzzy looking. Newer imaging software uses the process of interpolation which is a more intelligent way of choosing the pixels which are used as filler, but in general images which are scaled up more than ten or twenty percent lose much of their sharpness. Higher end imaging software programs use more sophisticated interpolation algorithms and tend to produce better results. Reducing the resolution of an image can generally be done to a much greater extent with no noticeable loss of quality. In order to reduce the resolution of an image, the imaging software must throw away pixels. Images can often be scaled down by more than fifty percent and still be of acceptable quality.
Resolution describes the amount of detail in an image, but the tonal quality of each pixel must also be considered. The pixel depth, also known as bit depth of an image, controls its tonal qualities. Milburn (2000, p.21) describes Apixel depth@ as bits per pixel because the amount of color information which can be assigned to each pixel depends on the amount of data that can be assigned to that pixel. A 1-bit image can only display black and white. To calculate
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