If you have ever had your printer or designer ask for vector graphics, and you had no idea what they meant, this article is for you. Here is a brief overview of vector and raster graphics.
Raster Graphics (pictures)
Common file extensions: .jpg, .png, some .pdf
Most digital pictures are made up of pixels. If you enlarge any picture enough, you will begin to see the pixels – square shapes with a uniform color. The smaller the pixels are the more that fit per square inch, and the smoother the picture looks when printed.
People often want to print a photo at a larger size than it was originally intended for. On TV, its a simple matter to “enlarge and enhance” any given photo (or video!). If you’ve watched CSI or similar shows, you’ve probably seen them “enlarge and enhance” a license plate, face, or other details. In reality, while you can enlarge a photo as much as you want, all this does is increase the size of the pixels. A small, blurry image will thus become a large, pixilated, blurry image. There is no “enhance” function. Similarly, printers cannot reduce the blurriness of your pictures. We can only use what is already there.
If your picture is good enough for the size you want to print it, your eyes will be unable to detect the pixels at 100% magnification. Another way to check your photo resolution is to view the file size. Most printed photos look better with a bigger file size. 20 kilobytes (kb) is generally too small for print at any size; photos larger than 1 megabyte (mb) are generally large enough to print on a 24”x36” poster with reasonable quality.
Of course, no matter what size your photo is, there is a size of printing at which you will see pixilation. That’s one reason we have vector graphics.
Common file extensions: .ai, .eps, .svg, some .pdf
Vector graphics don’t bother with pixels at all! Vector graphics are made up of lines and shapes. Using complex math, vector format files instruct your computer to draw a series of lines and shapes. Here are some benefits of vector graphics:
You can make them any size, and they won’t pixilate. 100% crisp, clean images.
The file size can be quite small and still have perfect clarity – easier to email.
Vectors can be used to create cutting instructions – for vehicle lettering, contour cut stickers etc.
Vectors can be used to create digitized logos for embroidery.
Vectors can be used by screen burning software for screen printed shirts and signs.
So, why would we ever use raster (picture) graphics? Well, cameras can’t generate vector graphics. Pictures of people and other complex color patterns cannot be made into vectors without loss of complexity. Also, vectors can be more difficult to work with without the right training or programs.
I hope this explanation helps – the more you understand about printing and design, the easier it will be for you to get what you want from your printer.