These changes have also increased the responsibilities of the graphics professional for print production. Designers are now required to take on duties that were originally performed by several highly-skilled individuals such as typesetters, photographers, darkroom technicians, etc. This means the designer also has to have an understanding of the myriad file formats used on the major platforms and the different uses and requirements of those formats. To complicate things, the rules are often evolving or changing as fast or faster than they can be mastered. Since there are so many variations, designers cannot just guess at or assume what is being asked of them.
Resolution is the number of units available to represent graphic detail in an image.
DPI is often used to refer to PPI, but that is incorrect and potentially misleading. Try not to resize images larger after they are scanned or shot, as this decreases the resolution you started with. Use the following guidelines in producing digital images for various output. So, if the screen ruling to be used to print the job is 150 lpi, the resolution of the graphics should be 300ppi. More than twice the LPI does not increase quality and will only slow down image processing.