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Production Series: Raster vs. Vector

May 24, 2010

Raster vs.Vector! Sounds like an epic battle between two comic book villains, doesn’t it? But no: raster and vector are simply two basic types of image files. And figuring out which one to use doesn’t have to be a battle at all.

The fundamental difference between raster and vector graphics is in the method the files’ data use to form the image. Each method has advantages for certain kinds of images.

Raster images, also sometimes called bitmap images, are made up of pixels: tiny squares of color that combine to form the image. Usually, these pixels are so small that you don’t perceive them individually – you just see the image they form. But if you zoom in extremely close on a raster image, you’ll see it’s really just a bunch of squares.

Raster images can contain many thousands of tiny squares of color.

Resolution is a measure of how many pixels are in a given area of an image. The more pixels, the more detail is visible in the image. When resolution gets too low, the eye begins to perceive the individual squares of color, lending the image a blurry or fuzzy look. This is typically something to avoid!

If the resolution is sufficient (which can depend on the medium; printed images require higher resolution than ones viewed on a screen), raster images excel at reproducing photos. They don’t do as well with line art or smooth curves, unless resolution is very high.

Vector graphics are composed of paths: The file describes specific points in the image and the paths that connect those points. This method allows vector graphics to be scaled to any size, because these points and paths are simply redrawn according to their mathematical relationships. Because there are no pixels, resolution is not an issue – no matter the size, vector graphics will always look just as smooth as the original.

Points and the paths that connect them make up the underlying structure of a vector image.

This is why vector files are usually preferred for logos. They can be enlarged to any size without losing quality – and even if they’re enlarged to huge proportions, the file size remains small!

The downside to vector graphics is that they don’t do as well with complex imagery that contains subtle gradations of tone or color – which means most photographs. There are always exceptions, but as a basic rule, stick to vector logos and illustrations, and let photos be raster.

–Austin Stahl, Art Manager, Network Media Partners, Inc.

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Filed under: design

Tags: images, print, production, raster, vector