Are Vectors Better Than Pixels?

This question could spark one of those classic feuds, such as the Capulets and Montagues, Macintosh versus Windows, or Burger King and McDonald's. People who create vector graphics often state that vector graphics are better than raster images. (Sandee, well known to her friends as Vectorbabe, has made her fondness for vector graphics quite clear. Steve, while not an official PixelPal, tends to enjoy working with raster images and their formats.)

As you work with the Creative Suite applications, it is important to know when you are creating vector paths and when you are creating pixels, and the benefits of working with each format.

Scaling Vectors or Pixels

Vector graphics are device-independent. This means that they can be enlarged several hundred times their original size without any loss of quality. That is what made PostScript fonts so revolutionary.

In contrast, pixel images, such as those taken by digital cameras, are device- and resolution-dependent; that is, they contain a fixed number of pixels. Scaling up a pixel image or printing it at a lower resolution than what it was created for can cause jagged edges (when the pixels are enlarged to fit the new size) or blurry details (when the program tries to figure out how to add new pixels to fit the larger image).

This is why many companies use vector programs to create their company logos. Vector graphics can be scaled up to any size without any loss of image quality. The mathematical formulas that define the image are simply adjusted for the larger-size logo.

Comparing File Sizes of Vectors and Pixels

Vector graphics create smaller files than pixel images. A six-inch, vector-graphic circle drawn in Illustrator creates a file only of 4.4K microscopic in computer file terms. In fact, the size of the circle is irrelevant; if you enlarge the circle, the file size doesn't increase.

However, a six-inch circle at 300 pixels per inch (ppi) in a pixel program creates a file of more than 12MB hardly an insignificant amount! And if you enlarge the size of the pixel image, the file size increases accordingly.

Choosing Vectors or Pixels

So which should you choose for artwork vectors or pixels? If you don't know the final size of the artwork, vectors are the clear choice. But other factors matter. Because vector artwork is made up of individual paths, it is much easier to modify. This makes vector the best choice for graphic designers, illustrators, technical illustrators, and cartographers in short, anyone who needs to alter the size, shape, and color of his or her artwork. For example, it is much easier to change the shape of a road if it is a vector path than an array of pixels.

Vector graphics also output with crisp, PostScript edges. This is what makes text appear to float, as if superimposed, over an image (see Figure 5-1). Of course if you don't want this effect, use pixel artwork. For instance, to add text to an image that looks part of the original photo, use text that is converted to pixels.

Figure 5-1. The House Tours text is PostScript (vector) text, The date on the house on the right is pixel text with slight blur added to help the text blend into the image.

Pixels are still the only way to capture images in scanners and digital cameras. Pixels are also the easiest way to create soft drop shadows, blurs, glows, and faded edges. Most textures also need pixels to look natural and organic. Can you create realistic illustrations with soft shadows and highlights using vectors? Yes; many photorealistic artists work exclusively with vector objects to create stunning images (see Figure 5-2). However, they have to work awfully hard compared to those who work with pixels.

Figure 5-2. Illustrator artwork created by Thomas-Bradley Associates using only vector objects.