Raster vs vector: Creating quality images

By Wendy Rall   Volume 2 Article 2

We've all seen it, a pixilated image. It looks bad, not just to you, but it makes the brand look bad. Understanding how images get pixilated, is the key to having the best quality possible for your brand’s photos and graphics, in both print and digital usages.

First I’d like toexplain that there are two digital files types: raster and vector. File types are not to be confused with file formats , which will be covered in a future article.

A RASTER image is a file made up of pixels. These types of files are made of “picture elements," the smallest point in the digital image, and is where the word “pixel” came from. Digital photographs are raster images. The more pixels you have in each square inch of your file, will determine the quality of that image.

Raster Image

A VECTOR file is made up of lines forming shapes that represent the image. There are no pixels in a vector file, therefore they do not loose quality when they are enlarged.

The quality of a raster press ready image, for offset printing is 300 pixels per inch (ppi). If you take an image with 300 pip and enlarge it, the pixels spread out, so there are less pixels per inch and the image quality decreases. 

If the image was created asvector, let’s take a logo for example, you can enlarge it as much as you desire and will not have loss of quality. This is why it is important to have your logo designed as a vector format. If your logo is designed as a raster image at seven inches wide, for example, and you want to use it on a trade show display or large banner, the image will deteriorate to the point that it is unusable.

Vector Image

When you are preparing an image for usage on the web, the requirement for a high quality image is 72 ppi, which is significantly lower than the requirement for offset printing. Digital print machines, both ink jet and laser, will provide a good print quality with a 72 ppi image, however if you can provide an image of 300 ppi it will be a higher quality print.

An important thing to consider when creating new artwork is how it will be used in the future. If you plan to use your logo or art in large formats, be sure that it is created as a vector, or at the usage size at 300ppi. 

If you have a photo that is “small” and you really need it “large” for usage on a banner, it is also possible to have a raster image converted to a vector image, this is a specialty type of artwork, and must be done by a qualified designer/illustrator. 

In closing, please know that this information is just the "tip of the iceberg". Be sure you are working with a designer who knows how to properly build your designs as well as format them correctly for various usage, which will be covered in the following weeks article.