When you are involved in the creation of graphics, you often have to decide whether to use a raster or a vector format. The following comparison between the two systems will give you some general information and help you to choose the appropriate format, according to your specific needs.

The following paragraphs will clarify some details of the raster and vector formats using a circle as an example. Imagine that you draw a circle with a graphics program.

The general difference:
Vector-based graphic elements are described by a mathematic formula and some additional attributes. For example if you were to draw a circle, you would need its center (in the form of a coordinate) and its diameter. Attributes can define the line weight, color etc..

Raster-based graphic elements are described by the order of single dots (also called "pixels") in a matrix. Here, attributes of the individual pixels describe diverse characteristics, such as color, transparency, etc..
 
Why vector and raster?
Both systems provide specific advantages. Pixel-based data is especially suitable for graphics where the color information changes from dot to dot. Photographs are a good example of this. Vector-based data is especially suitable for the creation of graphics containing elements like lines, rectangles, text, etc. These are always displayed plain, and the size of the whole graphic can be changed arbitrarily without loss of quality.

Where do vectors and pixels come from?
There are two groups of graphics programs: vector-based programs (i.e. IsoDraw, Adobe Illustrator, Macromedia Freehand, etc.) and pixel-based programs (Adobe Photoshop, Jasc Paintshop Pro, etc.). Depending on where and how you would like to use your graphics, each offers different advantages, as described above.

Display quality:
Due to the different systems, vector and raster graphics can differ in terms of display quality.
Vectors are always represented in the best quality, since apart from their invisible coordinates for the formula, they do not display fixed dots. The display quality of raster data depends on their zoom factor. This results from the pixel structure of this system: the single pixels become visible at a certain magnification and create the so-called "stairs effect" or "jagged edge effect". 

Special benefits:
Vector files offer flexibility. A line can be extended, a diameter can be changed or the elements can easily be arranged in a new order. This is especially useful in Technical Illustration because you can use an already created element in another illustration. Editing raster files in a raster graphics program is somewhat easy. With the eraser function, parts of elements can be deleted quickly. Finally, color gradients are a special strength of these programs.

File size:
Though storage media are not very expensive these days, data file size plays an important role, most notably in extensive archives. Raster files usually need more storage space than vector files. Currently, file size plays an importantant role, especially with graphics that will be made available over the Internet.

Portability:
Vector data can be converted into raster format without any problems. The reciprocal process, however, is not that easy. In some cases, the quality of the raster files suffers when they are repeatedly edited and converted within different raster formats.

Conclusion:
Use the advantages of both systems depending on the purpose of your graphics. If your graphics are not meant to undergo further scaling and the file size does not matter, it makes sense to use a raster format. However, if you wish to use your graphics in diverse media, scale them often and avoid double archives, a vector format would certainly be the right choice.