Dots Per Inch (DPI) is not the same thing as Pixels Per Inch (PPI) although there are many instances wherein these two terms are interchangeably used. Many print shops, graphic artists and magazines get it wrong when they talk about required digital photo resolution, mistakenly considering DPI when it’s PPI they really want.

In reality, the digital quality of a photo does not change due to DPI or PPI since resolution is about pixel dimensions. Some define DPI and PPI simply as a conversion factor used by software to set the paper output dimensions. When a photo needs to be resized, it is best to change the pixels.