The quality of a digital photo is determined by at least four main factors. The recording device’s quality specifically the camera’s optics and sensors and the scanner’s sensors affect to a large degree the resulting photo. Other factors consist of the size of the pixels of the digital image, the digital format it is stored in and the technical proficiency of the photographer.

Dots per inch or DPI should not be confused with resolution. The true resolution of a digital photo is simply the photo’s dimension in pixels. When a dimension is expressed for instance as 800 x 600 pixels, the first number represents the width while the second number represents the height of the photo.