A guide to vector and raster graphics
When you're talking about graphics, press quality artwork, PDFs, AI files, and all of that print related stuff, one thing that can be tricky to understand is the difference between raster images and vector graphics. For the highest quality, smooth, crisp printing results, you need to understand the fundamental differences between rasters and vectors, so we've put together this little guide to make it easier for you. Don't worry, though; we can help with how to set up artwork and graphic design if you're stuck and need a hand.
Vector graphics aren't some weird thing from outer space.
Vector graphics consist of intricate paths, lines and points. Scaling them to any size is made possible as the vectors are based on mathematical calculations, and regardless of how much you zoom in, it'll always look the same. There is no limit to how big a vector can be printed (apart from the limitation of the size the printing press or machine that's being used), and it will never lose quality.
You often see vectors being used for company logos, and in technical drawings (CAD), engineering, 3D modeling and animations. Vectors are often saved in the design industry as PDF, AI (Adobe Illustrator), EPS and SVG files. These types of files are best for laser engraving, etching, laser cutting, CNC routing, labels, decals and stickers, large format printing and metal stamping.
Then we come to raster images (also not from outer space)...
Unlike vectors, the raster format consists of an array or collection of pixels, each a different colour or tone, which, when placed together, form an image. You see this mostly in photographs, and you'll often see them saved as JPG, GIF or PNG files, which are all just common file types for raster data.
Blowing up or increasing the size of rasterised images.
Clusters of pixels can't be made bigger without losing quality. Every raster image has a certain number of pixels for every inch (also referred to as PPI; pixels per inch). As an example, a 300ppi image has 300 pixels for every inch. If you want to print an image that's 20x20 inches, and your printer asks you to supply images at a minimum of 300 pixels per inch (PPI), your image will need to be a minimum of 6000x6000 pixels.
You can't increase the resolution of images without losing quality.
While you can increase the resolution of images in software such as Photoshop, these photo editing programs achieve this by randomly generating pixels that closely match other, nearby pixels. While this might work for minor size adjustments, and sounds good, it's most likely that you'll end up with high resolution image that won't print or reproduce well.
What's the best format to save my files in?
If you're trying to provide high quality files for print, we recommend saving your files as PDFs with all transparencies flattened. All of the fonts in your documents should be outlined, and overprint should be turned off. Rasterised images within your document should always be at last 300dpi. For more detailed information, refer to our artwork setup guide.