Pixelation Example

Tip: Image Resolution for Print

How resolution works

Resolution is defined as the smallest interval measurable by a scientific (especially optical) instrument; the resolving power. Basically it’s a measurement of dots, in a single row, per inch. If you took a square and copied it, single file, from left to right for an inch you would have a pixel count. So if you had 24 squares in that inch you would have a resolution of 24 pixels per inch.

One of the most common place you see resolution from day to day. It uses dots of light know as a pixel; and has a minimum of 72 pixels per inch (ppi). The more pixels per inch the better quality image you will have and the more colors you can have. This allows you to zoom in without seeing any pixilation. We will talk about that in a moment.

Resolution on a printer is very similar. The big difference is a printer will drop little droplets of ink or toner instead of displaying dots of light. Dots of pigment that get dropped by a printer tend to be a little smaller then the dots displayed on a screen, so printers need a higher resolution. Printers have a minimum resolution of 300 dots per inch (dpi). Some printers can print up to 2400 dpi, but that’s only state of the art printers.

Why do you need to worry about resolution?

low resolution eye overlaid on top of high resolution photo
When this picture is blown up you start to notice the shape and color of individual pixels. When resolution is to low this is the effect you get. It happens both on screen and in print.

How can it affect my prints?

If your picture quality is too low you may not print what you want. For instance, if you take a picture you have as a 5″ x 7″ on screen with a resolution of 72 ppi, a printer will still print that picture at 300 dpi; cutting the overall size down to 1/3 of its original size.

What is pixilation?

close up version of Scarlett Johansson's eye
In this close up version of a low resolution picture we see individual pixels or dots. These dots when viewed from far away make a picture.

Pixilation happens when you take an image and blow it up. When you stretch an image without increasing the resolution you are literally making the dots the make that image bigger. The larger you make the image the more you can see each individual pixel, giving you pixilation.

Why does it pixilate?

Even with industry standard software computers lack the ability to predict what colors to use when you create a higher resolution. So they can only use the information they are fed. So once your image is at a set resolution it stays there.

What resolution do I need?

Designers are taught in school to use the highest resolutions possible. With today’s cell phone being capable of shooting over 4k (4000 pixels wide) image files become huge. So it’s nice to have an idea of your end project before you start.

You can always make an image smaller, but it’s incredibly hard to go the other way.

Basic rule of thumb is to design for your largest size of print and save a smaller version for screen applications.

So if you plan on making 5″ x 7″ post cards create a 5″ x 7″ document at 300 dpi/ppi. After that you can always save a smaller version. Most design software gives you a way to save a screen friendly version. Click here to learn more about file setup.