Every now and then you need to resize a photo for different reasons. Being an eager hobby photographer I like to be able to print some of my photos. Sometimes I want to make smaller prints and sometimes I want to make large ones. Storing different copies of my images would not be a space saver, so instead I use a different method: Scaling using DPI.
[disclaimer] This guide is written using Photoshop, but there are several other programs available with the same capabilities as described here (like Paint.net). This guide will not focus on how to create photos for use on the web where pictures need to be downsized and data removed.
To be able to resize a photo (making it larger or smaller) without removing data you need to know what a digital photo is and you will also need to know what DPI is and how it works. So let’s start with that.