Have you ever zoomed way in on a photograph online and noticed that it was made up of individual squares of color? These squares of color are called pixels. Pixels are the make up of raster based images, or raster graphics. Raster graphics are best used for non-line art images. Examples of these are digitized photographs, scanned artwork, and detailed graphics. Raster graphics can be very rich in detail because each square of color or pixel can be a slightly different color. This can create subtle gradients, much more detailing in shadows and highlights, and can intensify vibrancy.
The downside to raster graphics? Image degradation. Raster graphics are resolution dependent, meaning they are measured by pixels per inch (ppi). Let’s say you have an image that is a 1 by 1 inch square and there are 300 pixels in that area. If you want to blow that same 1 by 1 inch square into a 6 by 6 inch square, there are still only 300 pixels in that image. This means those same 300 pixels have to cover six times more space. This is why sometimes images look jagged, and you can see individual pixels. This degradation is called bitmapping. Bitmapping is the reason that Logos should not be made by raster based software, the most popular being Adobe Photoshop. Raster images can be scaled down more easily, but it will not look as crisp as the original.
So what is the best way to create a logo? Vector based graphics software, the most popular being Adobe Illustrator. Vector graphics are created using lines and points to create shapes. These lines are created and managed using mathematical formulas to create lines, points and shapes. Like numbers, there is no limit to how large or small you can make a vector graphic. It can be made large enough to take up a whole billboard and small enough to but on a business card without ever loosing image quality.
Type is a vector based graphic. That is why you can have one-point font and blow it up to 6400 points and still have crisp edges.
One downside to vector graphics is they can lack detail. If you draw a square and fill it with blue, the whole square is blue, leaving no room for gradients. In order to get a true vector gradient, you would have to create smaller and smaller rectangles at slightly different shades of blue.
Another down side of vector graphics is the limit of effects. They are created using simple lines and points, with no pixels. Therefore, they can’t handle certain styling effects, such as drop shadows or inner glows. It is possible to get raster based effects such as drop shadows on your vector image. This does, however, make the whole file a raster based image. It is still more scalable than a raster based image, but the effect can be bitmapped when blown up.
The last difference between Raster and Vector graphics is file size. Raster images, as I said before, are made up of pixels. If you have an image that is 18x24in and it has a resolution of 300 ppi – that’s 129,600 bits of information that has to be saved. This means files sizes can get huge really fast. Vector graphics on the other hand, only has the points and lines to be saved, witch can mean much smaller file size.
So, if you are looking for rich detail, or lots of fancy effects, than raster is the way to go, but if you are creating a logo that needs to scale to multiple sizes vector is the best option.