Pixels, Dots, DPI and Print Resolution Explained

Pixels and Dots

A dot or a pixel are what we call a single building bock or unit of colour which makes up an image. The images below are constructed from different numbers of pixels/dots.

Resolution

Resolution describes the level of detail and sharpness in an image and is defined by measuring how many dots or pixels there are in a given linear unit (for example 5 dot/pixels per millimeter or 6 dots/pixels per inch). An image with a large number of dots/pixels will appear clearer and sharper than an image of the same size with fewer. We would describe this first image as being higher resolution and the second as being of a lower resolution. Let’s demonstrate this by taking the shapes from our last example and making them all the same size.

Print Resolutions Explained

It is common convention in the printing industry to talk about resolution in terms of “Dots per Inch” or “DPI”. In the case of printing the word dot refers to dots of ink which form the building blocks of all printed images.

So far we’ve had some examples of images with 6 pixels per unit but in order for your art work to come out looking as beautiful as possible printers require artwork supplied to them at a resolution of at least 300 DPI. That’s an unbelievable 90,000 droplets of ink per square inch of your image meaning that one single double sided A6 flyer alone contains an incredible 4,280,400 droplets of ink.

So how does this tie in with computer resolutions and designing artwork? People often ask me why the images hey have to design on their screens appear so much larger on their computer screens than they are in print. Why can’t an image which measures 10 inches by 10 inches on my computer screen (and looks absolutely perfect) be printed out the same size?

The simple answer is that computer monitors have comparatively low resolutions (usually between 80 - 180 pixels per inch). My Mac Book squeezes 1920 pixels across the screen’s 14.42 inch width meaning it has a resolution of 1920 pixels / 14.42 inches = 133 pixels / inch. This means that I can only fit 300 pixels in to 2.25 inches ( 300 / 133 ) so each 2.25 inches on my screen will translate into one inch once my product is printed!

To make things easier we’ve put together a table of Common Paper Sizes, Names, Measurements & Templates for your reference!