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Digital Printing Explained 2 – PPI vs DPI

Digital images are created by a grid of colored pixels.  The number of pixels in the grids x and y dimensions determine the resolution.  This creates and easy to use system as a 3MP image with a resolution of 2048x1536 will always have 3,145,728 pixels, regardless of the colors used in the image.  The Pixel Per Inch system gives a relation between pixels and print size.  This allows a certainty of print size as a 300ppi images will always represent 300 pixels per inch, so a 1000x1000 pixel image at 250ppi will print at 4” x 4".  Typically each pixel can be any of 16.7 million colors from either the Adobe RGB (1998) or sRGB colorspaces. The 16.7 million colors is based on 8bit RGB images where each pixel can have any color created by 255 shades of each Red, Green and Blue (255 * 255 * 255).