Understanding DPI and PPI
DPI (Dots Per Inch) measures how many ink dots a printer places per inch of paper. PPI (Pixels Per Inch) describes how many pixels are packed per inch on a screen. Although different in origin, the two terms are often used interchangeably in the digital imaging world.
Most digital cameras save images at 72 or 96 DPI by default, which is fine for screens. However, professional print shops typically require 300 DPI to ensure sharp, artefact-free output. Here’s why DPI matters:
- Print quality — below 300 DPI, printed photos may look blurry or pixelated.
- File preparation — many print services reject files under 300 DPI.
- Web performance — images above 72–96 DPI are unnecessarily large for screens.
- EXIF metadata — DPI is stored in the XResolution/YResolution EXIF tags and can be read without modifying the image.