A common question arises whenever the topic of graphics comes up. Which file format should be used to create a successful project? There are many different graphic file formats existing, almost as much as graphic software packages. However they can all be divided into two types, vector and raster.

Raster graphics are images made of pixels or "bits" organized in a grid system. Each individual square pixel is a separate dot of colour, and when combined together create an image. The number of pixels in an image determines its quality and is typically measured in inches. In the graphic industry the number of pixels in an image is referred to as "dots per inch" or "dpi". The more pixels per inch your image contains the sharper your image will look. Higher quality images use more computer memory and result in a larger file size. For example, graphics meant for online purposes, such as web graphics, require low resolution (72 dpi) because normally they are viewed only on a computer monitor. Most computer monitors will only display 72 dpi, therefore, higher resolution will only increase the file size of the image without yielding any visible improvement to the image. On the other hand graphics meant for print purposes, such as an art magazine, require higher dpi for better quality and sharper printouts. However, the file size of such an image would be greater because more pixel information is required.

The dpi of a graphic in raster format is fixed. This can cause problems when trying to resize the image for larger scale projects. If a 300 dpi image with a width of eight inches and a height of eleven inches were scaled to billboard proportions, the pixels would appear to grow, filling the required space. The smooth lines and curves of the original image become jagged, geometric and in some cases undistinguishable. For example, an image of a human face becomes distorted and abstract. Instead of blending together to form the face, each individual square pixel becomes obvious because of its increased size.

A 72 DPI Raster Image Scaled 600%

Unlike raster graphics, vector graphics are made up of individual scalable objects. These objects are created using mathematical equations, lines and shapes, instead of pixels. Each object in the graphic can be treated separately because it has its own individual properties assigned to it such as colour, fill and outline. For example an artist can easily move the position of a title in a layout from the top of a page to the bottom because all the objects in the layout are created separately. If the layout were in raster format this would not be so easy, because once a colour pixel is placed on a canvas it is fixed. To move a pixel around in raster format, features such as Adobe Photoshop's "layers" must be used.

Since vector graphics are not created using pixels, they are resolution independent and are easily scaled to any size without looking jagged and blurry. For example a vector graphic scaled from eight inches by eleven inches to billboard proportions would still retain its crisp and sharp features.

A Vector Image Scaled 600%

Vector graphics are fairly small in file size in comparison to raster graphics because they use mathematical equations instead of pixels. To create a vector circle, the only information required is four coordinate points and four angles. A rastered circle on the other hand requires information for each and every pixel. The more pixels used to create the circle, the more memory from the computer is required.

Vector graphics can be converted to raster graphics quite easily using simple "Save As" methods. This process is called rasterizing. Converting raster graphics to vector is a little more challenging and requires software packages such as Adobe Streamline to determine the edges in the graphic in order to create objects.

One reason vector graphics would be converted to raster graphics is for online purposes.

Raster images are the ideal format for photography, texture, and computer generated painting because each pixel can be rendered to show subtle gradation of shades and colour, something vector graphics lack because they generally have large fill areas of solid colour or gradients and tend to have a cartoon-like appearance.

Vector graphics are best used when creating logos and type intensive layouts requiring clean lines, smooth curves and the ability to be displayed in a variety of sizes. It is also the ideal choice to use for 3D modeling which requires the manipulation of objects over and over again when designing.

Paint programs such as Adobe Photoshop and Paint Shop are used to create raster-based graphics. Typically raster formats are JPEG, GIF and BMP. Drawing programs such Adobe Illustrator and CorelDraw are both vector-based programs that create vector file formats such as EPS and AI.

When designing your graphics keep in mind that the file format you use will make a big difference when it comes to the success of your projects and what you will be able to use them for. So take the time to choose the right format because it will save you time and money.