Example of Unacceptable Resolution
Files created in Raster format are made up of little squares of color called pixels, The amount of squares in an inch is a measurement referred to as resolution or "dpi" (dots per inch). Once the digital file is at a low resolution, the detail is lost. You can not add pixels to clear it up. It only makes it worse. 300 dpi at full size is a good quality file to work from. If the file is 300 dpi at 3 inches when you size it to 9 inches it becomes 100 dpi.