Vector graphics. Raster images. If you’re not involved in graphic design at all, you may be wondering what in the world those words mean. Here’s an explanation in a nutshell.
Raster images are made from pixels. Digital photographs are raster images. If you have a photograph on your computer and you zoom way in, you’ll probably be able to see all the individual colored blocks (pixels) that, together, create a complete image. If you try to enlarge a raster image from its original size (without proper tools), this usually results in it becoming “pixelated,” where the image looks blurry or distorted because the pixels are visible. If you’ve ever tried to enlarge a picture in, say, Microsoft Word, you may have encountered very low quality. This is because the number of pixels in the image are not being multiplied – they’re just being stretched out of proportion. The result is jagged edges that looks less than professional. Outside of professional work, the best rule of thumb is to never enlarge a raster image. You can shrink an image without destroying quality, but enlarging it will usually end in something that looks less than desirable. This is why using the highest quality image in the first place is generally best. You may work with a lot of .jpeg files – those are all raster images.
Vector graphics are made up of mathematically based paths. That is, lines that are mathematically constructed so that when you enlarge or shrink, the quality is not compromised. For example, a company logo may be designed at 4” x 4”. But it can be enlarged to fit on the side of a truck or a building – without the trouble that pixels bring along. Special programs are needed to create vector graphics, such as Adobe Illustrator. These programs are specifically designed for this purpose. You may see file types such as .ai, .svg or .cdr. Note, however, that simply dragging a vector graphic into a Word file may not work as you’d expect. It may be rasterized upon insertion, which means you’re back to pixels again. There are tutorials online on how to insert vector graphics into your Word documents, but the best policy, again, is to have a larger-than-needed image which you can make smaller if needed, and avoid a lot of headaches. Now, if you’re wishing to use an image for digital purposes (an email signature, use on a website page, etc.) you will most like need to upload a raster image like a .jpeg or .png.
A quick recap: raster images are composed of pixels, while vector graphics are composed of mathematically constructed lines/paths. Each file type has its place with different sets of pros and cons.
This is an example of a vector graphic next to a raster image. However, the entire piece has been rasterized (made into a .jpeg, enabling it to be uploaded to this blog post).