Difference between File Types
If you’re confused over the difference between the many image file types, you’re not alone. When starting off a project, one of the first things we request from the client is a vector file of their logo. However, that request is often met with blank stares or responses like “can’t you just pull the logo from my site?”. Understanding the importance and role of different image file types is essential to ensuring your brand is properly represented and to better communicate with designers, developers and printers.
What is a vector file? What is Raster?
We can start making sense of the issue by clarifying the difference between the two major image types – raster and vector.
Raster images use many colored pixels or individual building blocks to form a complete image. JPEGs, GIFs and PNGs are common raster image types. Almost all of the photos found on the web and in print catalogs are raster images.
Because raster images are constructed using a fixed number of colored pixels, they can’t be dramatically resized without compromising their resolution. When stretched to fit a space they weren’t designed to fill, their pixels become visibly grainy and the image distorts. This is why altered photos may appear pixilated or low resolution. Therefore, it is important that you save raster files at precisely the dimensions needed to eliminate possible complications. These are rarely usable in the sign industry.
Vector images, alternatively, allow for more flexibility. Constructed using mathematical formulas rather than individual colored blocks, vector file types such as EPS, AI and PDF* are excellent for creating graphics that frequently require resizing. Your company logo and brand graphics should be created as a vector and saved as a master file so you can use it with smaller items such as your business card and letterhead, but also on larger surfaces, such as your corporate jet. When necessary, always create a JPG or PNG for use on the web from this master vector file. Just be sure to save the new raster file in the exact dimensions needed.
*A PDF is generally a vector file. However, depending how a PDF is originally created, it can be either a vector or a raster file. Whether you opt to flatten the layers of your file or choose to retain each one will determine the image type.
File Extensions to look for:
EPS An EPS file is a vector file of a graphic, text or illustration. Because it is vector it can easily be resized to any size it needs to be. An EPS file can be reopened and edited.
Best use = master logo files and graphics and print designs. AI An AI file is a proprietary, vector file type created by Adobe that can only be created or edited with Adobe Illustrator. It is most commonly used for creating logos, illustrations and print layouts.
Best use = creating logos, graphics, illustrations.
Editing vector files and saving “in outlines” Vector files such as AI and EPS can remain editable so you can open them back up in Illustrator and edit any text or other elements within the graphic. With images that contain text that are saved as a JPG, PNG or GIF, you would not be able to reopen and edit the text.
Saving in “outlines” is a term that you will hear when sending files to print. If a printer doesn’t have a font you used in your design and the vector file is not saved in outlines then when they open the file the text won’t have the desired look as it will default to a different font. Saving something with “outlines” basically means you are locking the text so that it’s no longer technically a font but instead made up of vector shapes that form your letters. This is important when sending graphics to print.
Working with images can be confusing, but bearing these key facts in mind will eliminate much of the hassle and of course we’re always here to help or answer any questions.