Understanding Resolution for Digital Photography, Graphic Design and More

"72 PPI."

"300 DPI."

"1500 X 1500."

These terms all appear different, but they all refer to the same thing. Resolution. So it's no wonder many people are confused by the details of resolution. If you are interested in digital photography, graphic design, or selling your own t-shirt designs on the internet, it's important to have a grasp on the concept of resolution so your images look professional. Read on for a crash course in understanding resolution.

You have probably seen the term 72 PPI. Most computer monitors display images at a resolution of 72 PPI or pixels per inch. That means that every square inch on your monitor contains 72 pixels. A pixel is a tiny little square of light, and thousands of them are combined to make the images you see on your screen. Most monitors are not capable of displaying more than 72 PPI, so most images you see on the internet will be optimized for display at that resolution.

If you have ever downloaded an image from the internet and printed it, you may have noticed that when it came out of the printer, it didn't look that great. It probably looked jagged and blurry. That's because in order for an image to look good on paper, it needs to be printed at 200-300 DPI. DPI and PPI are basically the same thing, except that DPI stands for dots per inch, and refers to the printed resolution of an image.

PPI=Pixels per inch and refers to screen resolution.

DPI=Dots-per-inch and refers to printed resolution.

That's easy enough to remember. But there is a third way of referring to resolution and that is the images' total size in pixels. If an image is 1500 X 1500 that means that it is 1500 pixels wide and 1500 pixels tall. Those numbers are fixed, meaning that unless you crop the image or add more space, it will always be 1500 X 1500. DPI and PPI are arbitrary. If you upload that image to display on a website at 72 PPI, it will be nearly 21 inches wide and 21 inches tall. (1500/72 = 20.83) If you print the image and select a print resolution of 300 PPI, it will be 5 inches wide and 5 inches tall. (1500/300 = 5)