What is a vector? What is raster?

If you’re confused over the difference between the many image file types, you’re not alone. When starting off a project, one of the first things we request from the client is a vector file of their signs. However, that request is often met with blank stares or responses like, “Why can’t your graphic designer pull my logo/design from my document such as a JPEG or from my website?”.

We can start making sense of the issue by clarifying the difference between the two major image types – raster and vector.

Raster images use many colored pixels or individual building blocks to form a complete image. JPEGs, GIFs and PNGs are common raster image types. Almost all of the photos found on the web and in print catalogs are raster images.

Because raster images are constructed using a fixed number of colored pixels, they can’t be dramatically resized without compromising their resolution. When stretched to fit a space they weren’t designed to fill, their pixels become visibly grainy and the image distorts. This is why altered photos may appear pixilated or low resolution. Therefore, it is important that you save raster files at precisely the dimensions needed to eliminate possible complications.

Vector images, alternatively, allow for more flexibility. Constructed using mathematical formulas rather than individual colored blocks, vector file types such as EPS, AI and PDF* are excellent for creating graphics that frequently require resizing. Your sign, logo and brand graphics should be created as a vector and saved as a master file so you can use it with smaller items such as your business card and signs, but also on larger surfaces, such as your corporate jet. When necessary, always create a JPG or PNG for use on the web from this master vector file. Just be sure to save the new raster file in the exact dimensions needed.

*A PDF is generally a vector file. However, depending how a PDF is originally created, it can be either a vector or a raster file. Whether you opt to flatten the layers of your file or choose to retain each one will determine the image type.