Xerox Phaser EX7750 Reference Guide

Print the files and examine the output. You will likely begin to see a marked 
deterioration in output quality at resolutions below 200 ppi, while above 200 ppi the 
improvement may be very subtle. 

Raster images prepared for offset printing may need to be at higher resolutions than 
necessary for proofing on your Color Server.

Ideally, each raster image should be saved at the actual size, and it will be placed in the 
document at the optimal resolution for the printer. If the image resolution is correct 
for the printer, there is no quality advantage to be gained by scaling an image to a 
percentage of its actual size. If you scale a large image to a percentage of its actual size, 
you incur unnecessary file transfer time, because the image data for the entire large 
image is sent to the printer. If an image is placed multiple times at markedly different 
sizes in a document, save a separate version of the image at the correct size for each 
placement.

If you need to place an image at greater than 100% in a document, remember that the 
output image resolution is affected. For example, if you scale a 200 ppi image to 
200%, the image is printed at 100 ppi.