Raster Image versus Vector Image

The following explains the difference between a rastor image and a vector based image.  The important point to remember is that each image is suitable for particular graphical reproduction purposes.  

Vector Image

Raster Images

Raster images are made up of dots. Often you hear the term DPI which stands for dots per inch. If you were to enlarge a photograph up on the computer screen you would see these dots. The higher the dpi or resolution the better the quality of image. File compression can help reduce raster image file sizes down but generally the file sizes will be large for quality high resolution rastor images. Important for repoduction. If DDP were to print for instance a photograph onto acrylic the quality of the original image supplied is vital. If you the client supplied a low resolution, low dpi image the repoduction we can achieve is only as good as your image. If DDP have to enlarge the image from a low resolution,low dpi image the quality becomes worse. In fact any raster image enlarged loses quality. Imagine a group of fine dots. Now double the size of the image and the dots/space increase in size and you begin to see a much courser looking image. Its the difference for instance between a photo in a magazine or a photo in a newspaper. The latter looks much courser as the quality of image used to produce it contains less information..ie few dots per inch.