Scanning images for the Web has very different scanning requirements than for Print. The main difference is in the dpi (dots-per-inch) required for a good scan.
Images for print should be scanned in at 150-300 dpi for a fairly good print and reasonable file size. However, an important fact to remember is this: The higher the dpi, the higher the file size. This means that you will want to decide on the minimum acceptable quality and the maximum file size you can handle (storage-wise).
For example, if you have an element in your design that will be printed very small, you do not need to scan that object in at 600 dpi. The resolution or visibility of the object may be such that the viewer will not be able to see it clearly no matter how high the resolution is. The same goes for elements that will be blurred; perhaps a smaller resolution would work better in those cases.
On the same note, if you intend to do a lot of manipulating of the image, such as resizing, or distorting, you may want to start out with a higher file size in order to maintain a good quality.
When scanning for the Web, it is important to note that computer monitors display images at 72 dpi. Therefore, it is best to scan the image in at 72 dpi, unless you need to make major modifications. This insures that you not only get the best file size possible, but you get a better idea of exactly how the image will show up on the screen. If you work with files that are at a higher resolution, the images will appear larger on the screen (in addition to having a larger file size).
|Properties of Printed Images
||Properties of Video Screen Images
|Image size is measured in inches
||Image size is measured in pixels
|Image size does NOT vary with scanned resolution
||Image size varies with scanned resolution
|Image size is modified on paper by scaling
||Image size is modified on screen by resampling
|Image pixels are spaced on paper using specified scaled resolution
||Image pixels are located at each screen pixel location, one for one
|Several printer ink dots are used to represent color of one image pixel
||One screen pixel location contains one image pixel, and can be of any RGB value
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