SCANNING IMAGES

RESOLUTION
The resolution at which your image is scanned is dependent on two things:
(1) the method by which the image will be output (web page, laser printer, copier,
small press, large press, etc.) and
(2) the amount of resizing required.

A rule of thumb is to scan your image at twice the line screen of your output device.
Here are some examples of typical line screens and subsequent scanning
resolutions for common methods of reproduction:

     REPRODUCTION                LINE SCREEN              SCAN RESOLUTION
         Laser Printer                               50 lpi                                   100 dpi

         Newsprint                                    85 lpi                                   150 dpi

         Color Copier                               100 lpi                                  200 dpi

         Offset Printing                            150 lpi                                  300 dpi

         Web page                                      N/A                                 72 - 75 dpi

Also, you must also compensate scaling (increasing or decreasing the size of the original).
For example, if you want the printed image to be twice the size of the original, you would
scan the image at twice the resolution.
The optimum resolution to scan your image is found by combining both
reproduction method and scaling. The result is the following equation:
Scan resolution=(lpi of output device x 2) x percentage increase/decrease of
image size.
For instance, let's say you have a photo that is 2" x 2".  You will have your
brochure offset printed (150 lpi). And you want to ultimately reproduce this photo
in a brochure at 3" x 3" (a 150% increase).
Using the formula above, doubling the line screen of the output device (150) gives
you a resolution of 300 dpi. However, scaling the photo by 150% requires a final
scan of 450 dpi.

GAMMA
   The most common error designers make when scanning is generating scans which are too dark
or too light. This is usually a function of the designer's monitor. A poorly calibrated monitor will
not provide a true picture of the scan .
   To correct this, do a test. Scan an image at various levels of gamma. Place them in a page
layout document and have a high resolution PMT made of the file.  Compare the image setter results with your monitor and adjust accordingly.  More importantly, learn to use the "Show Info" dialogue box in Photoshop. The levels of gray or density of color in an image will give you a good idea how much ink is going on the page.  Generally, most scans and CD images need to be lightened. Use the Photoshop "Levels" or "Curves" functions to adjust for lightness or darkness.

SHARPENING
Generally, most scans and CD images also need to be Sharpened.  Use the Photoshop "Sharpen" or "Unsharp Mask" functions to make your images clearer. But remember not to sharpen an
image too much.