During every graphic design class we run at the Digital Workshop Center, there’s almost always a lengthy discussion about image resolution.
Imagery used to be so simple when the world was still analog. But with digital imagery, there are many factors to consider when determining resolution.
First, to understand resolution you need to understand that all digital images are made of pixels, which is short for “picture elements.” A pixel is the smallest meaningful unit in an image and holds all of the color definition information, including color and brightness.
When you group a large amount of pixels in a small area, you begin to represent an image into something the eye recognizes. The more pixels in an area, the better the quality of the image.
This quality is what we call resolution and is typically measured in pixels per inch (PPI) on a computer screen. On a printed photo, it’s often measured as dots per inch (DPI) because printers originally measured in dots, not pixels.
When referring to resolution from a digital camera, we’re really talking about how many pixels per inch the camera can store in one image. This is typically measured in megapixels, which multiplies the total width and height pixels of an image. For example, an image that is 4,368 pixels by 2,912 pixels is said to have 12.7 million pixels, or 12.7 megapixels.
For most digital images that need to be printed, we use 300 DPI as a standard because it’s what’s been determined to be enough for the eye to view the image and effectively determine that the image looks correct.
Printers work by putting ink or toner onto a piece of paper. A printer’s possible output is measured in DPI due to how the printer moves the ink head across the page. Inkjet printers drop a dot of ink as needed, while laser printers melt a drop of toner to the page. The more dots you fit onto a printed page, the higher the resolution of the printer.
You may ask, “What’s the right resolution for me?” Unfortunately, there’s no one right answer. For everyday printing of basic documents, you don’t need to print at a high resolution, as it would be a waste of ink. You need to think about each step in the digital chain of events from capturing the image to printing it, and then determine what resolution makes the most sense for your situation.
[Originally published in The Coloradoan on 7/25/13]