There are two primary types of images used in print and other applications: Pixel-based raster images and line-based vector images. The unique characteristics of each type of image dictate how each should be used. This guide will help you understand the difference between the two - and the proper application of both.
Raster images, probably the more well-known of the two types, are the common, pixel-based images that we see all over the internet. Raster images are the types of images you get from a digital camera or the camera on your phone; the same goes for images pulled from documents via scanner. The common image file types on the internet – jpgs, gifs, and the like – are generally raster images. Any image that’s made up of pixels – the tiny, individually-colored units that combine to make the whole image – is raster. This is why these images blur when enlarged: A close view of the image reveals the individual pixels that make the image and breaks the appearance of a smooth transition across these pixels. This blurring is called pixelating. We’ll revisit this idea later.
Raster images are still the best form of image for photographs, especially regarding editing functions from software like Photoshop, designed to work well with the pixel-based format. It’s possible, of course, to print raster images at different sizes, but the pixel count in the image needs to meet a minimum that correlates with the size of the piece being printed.
Vector images are different from raster images. First, they aren’t made up of pixels. Vector images, which are generally made or translated through illustration software, are actually made up of individual lines and shapes (called objects) that combine to make a whole image, through mathematical calculations that define the shapes and directions of the lines.
Vector art is not created through a camera; instead, it’s created through illustration software like Adobe Illustrator and Corel Draw and commonly saved as .ai, .pdf, .eps and .svg files.
Although vector images lack the complex details that you can create with photographs (raster images), vector art shines in it’s own way: Recall the earlier reference to pixelation. You won’t find any in a vector image, no matter what size the image is stretched or shrunk to.
This is why vector images are an excellent format for the creation of printed products such as postcards, brochures, banners, and signs. Logos or illustrations as a vector image can be stretched to any size for printing without losing image quality or ever seeing any blur or pixelation, which means your graphics will look great regardless of whether they’re printed on small business cards or jumbo-sized banners.
Vectors, for this reason, especially shine for the creation of company logos, because one image file can be used for any application, regardless of size or printing medium.