There's often considerable confusion over image resolution and what's required when it comes to using images for print and the internet. An image is made up of multiple condensed dots, of which to the human eye looks like a smooth colour / visual. Using a magnifying glass you can see the image is made up of micro dots. The term for image resolution is called DPI - Dots Per Inch.
Dots per inch determines how small the dots an output device will use when printing an image. A 300dpi laser printer uses black dots that are 1/300th of an inch in width.
So, each time we use an image we need to understand how many dots are we fitting into every inch of the image to create the full image resolution.
- For the use of an image on the internet, the industry standard resolution is 72dpi.
- For the use of a Printed Image, the industry standard resolution is 300dpi.
If you print a 72dpi image on a Leaflet, (which requires 300dpi) you will get an image printed that is low resolution and will display pixelated.
If you use a 300dpi image on the internet, (which requires 72dpi) your website will start to run slowly and the images will take a long time to load, slowing down the entire website.
You can scale down an image (From 300dpi > 72dpi) you cannot increase the DPI.
So if you have a photograph you wish to use on the internet, ensure you're NOT saving over the original when you save as 72dpi. You can't reverse this process, If you try to increase the image resolution you will get the same outcome as in print and have a low resolution image that displays pixelated.