What resolution should my file have?

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Print is made up of dots. The number of dots per inch (1 inch = 2,54 cm) is called the resolution of the printed matter, this is expressed in DPI (Dots Per Inch). The more dots (and therefore ink) on an inch, the higher the resolution and the sharper the image. For printing, the optimal DPI is 300 and the minimum DPI is 150.

However, the term DPI is very often misused. Images that you see on screens are not displayed in dots, but in pixels. Therefore, the resolution of a digital image is expressed in PPI (Pixels Per Inch). Images you find on the web generally have a PPI of 72. Images with this resolution are too low in quality to print. Figure 1 shows the difference when printing an image with 72 and 300 PPI.


Het verschil in drukkwaliteit van een afbeelding met 72 en 300 PPI
Figure 1: the difference in print quality of an image with 72 and 300 PPI