File Types: Raster vs. Vector Explained

The Underlying Difference

Graphic files exist in 2 varieties: VECTOR and RASTER. These terms refer to the construction of the file and how the software created the shapes displayed.

Raster Files

RASTER is the format used to save photos. The most familiar extensions would be jpg, tif, psd, gif or bmp. These graphics are made up of pixels or dots. Each pixel is assigned a specific colour and a size determined by the resolution set at the time of saving. Scaling a RASTER enlarges each pixel and they become more obvious as you can see below.

Here is a close-up of a raster version of our design squirrel’s tail:

If it becomes necessary to edit the colour or shape of this graphic, each of these pixels will need to change. As you can see, there are many colours that make up what appears to be black or white. To change a colour, all the affected pixels must be captured. This often means having to redraw the shapes before applying a new colour. Ironically, editing a RASTER involves creating VECTOR shapes.

Vector Files

VECTOR files are created by draw software like Illustrator or CorelDraw. You may be familiar with the extensions ai, eps or cdr. These graphics are made up of points, lines and shapes. They can be stretched to any size because the lines and shapes scale independently from the file resolution.

Here is our design squirrel again, showing the vector shapes making up the tail:

Changing the shape of this graphic means a click and drag; changing a colour is a simple selection of a shape and application of a new colour.

Nutshell Comparison

Both formats have their advantages and disadvantages. The limitations of each are often dictated by the underlying construction. Raster files are compatible with a wide variety of software, but can be difficult to edit and may not scale up to the size needed. Vector files may not preview or open in all applications, but are easy to edit in the proper software and maintain clarity at any size. See our blog entry “Why can’t you just use my jpg?” for more information about when a vector might be the better option.