A picture is worth a thousand words but is a fuzzy picture worth any words at all?
Unless an editor is also a photographer or production staff, the only time they are likely to run into image resolution details is when previewing an image or making an image request.
Resolution is a term used to describe the number of dots or pixels in an image; it relates to how clear and sharp the image looks. Pixels per inch (ppi) is the measure used when describing images displayed on a screen; screens are made of pixels. Dots per inch (dpi) is the measure used for images printed with ink ok paper. Literally, it’s a measure of the number of ink dots per inch in the printed image. Like the tech version of a pointillist painting technique, you can see those dots by holding a magnifier up to any image on paper. You won’t see dots on photographs printed in a photo lab because those are made from light-reactive paper rather than ink. Pixels are basically the electronic dots that make up an image on screen. In practice, dpi and ppi are used interchangeably.
Printed images should come from files that have a resolution of at least 300 dpi to look clear. The size of the image file depends on how big the final image will be because there are 300 dots in each linear inch in the photo; 90,000 dots per square inch.
Images destined for screen display should have at least 190 ppi. In the early days of the World Wide Web, 72 dpi was the standard resolution for images. It meant that images were clear and file sizes were as small as possible to make downloading fast. But with today’s HD, 4K, and Retina screens, users will notice a loss of clarity in images under 190 ppi.
The lower resolution that looks good onscreen explains why images taken from a website look so bad when printed—like the one shown in this post.
This article was originally posted to Copyediting.com on 11/5/18.