image file definitionsHave you ever wondered what those funny looking file names mean whenever you save something to your computer? What’s the deal with those extensions like:

  • .pdf
  • .jpg (or .jpeg)
  • .gif
  • .psd and son on

They can be really confusing but extremely important depending on what you’re doing.

Image files can be broken into two categories, Vector images and Raster images. Let’s get started breaking it down.

Raster Images

Whenever you save pictures you find or purchase online, you’ve probably noticed that the save type is usually a JPEG (JPG), PNG or GIF. These are all considered raster files. Raster files; also referred to as bitmaps, are constructed of a grid of pixels or points of colors to make images view-able on computer monitors and paper.

As long as raster files remain in their exact dimensions; it will retain its quality. Re-sizing raster files will cause the images to become distorted and blurry.

Vector Images

Vector images are based on mathematical expressions by using points, lines, curves, and shapes to display images. This is perfect for people who are going to have to re-size images on a regular basis. Vector images are saved as a PDF, EPS or AI.


With the emergence of HD and Ultra HD resolution on televisions, smartphones, computers and tablets, high-resolution is becoming a necessity. Designers have to figure out what DPI (Dots per inch) or PPI (Pixels per inch) is needed for their images.

Often times DPI and PPI are used interchangeably but they shouldn’t.  If a picture has a low number of DPIs; that may work perfectly for the web but may be distorted if the image needs to be printed.  When it comes print, a higher DPI has to be used to achieve the same clarity.

As for PPI, if you’re only going to be viewing an image on a monitor; there is no need to make changes to the image, the PPI is already fixed within the monitor. You have to be very careful when dealing with PPI because tampering with pixels can totally change an image. In order to increase the resolution of an image, you have to produce more pixels, not increase the PPI.


JPEG (file name extension .jpg or .jpeg) Joint Photographic Experts Group

JPEG is the most common format for storing and transmitting photographic images on the internet. They are a commonly used method of lossy compression for digital images.

GIF (file name extension .gif) Graphic Interchange Format

If you’ve ever been on Tumblr you’ve probably seen a GIF. Animated GIFs are commonly used for file types where there is more emphasis placed on the load speed of the image versus the quality of it. GIFs allow a single image to reference its own palette of up to 256 different colors chosen from the RGB color space.

PDF (file name extension .pdf) Portable Document Format

PDFs are great for sharing because they can present documents without having to use any application software, hardware and operating systems.

PSD Adobe Photoshop

Adobe Photoshop is a raster graphics editor. Photoshop has become so popular for its editing ability that it is often used as a verb. It has limited abilities to edit text, vector graphics, 3D graphics and video.

AI (file name extension .ai) Adobe Illustrator Document

Designers prefer AI when creating artwork from scratch. It is perfect for tasks such logos because it is easy to manipulate since it uses vector images.

EPS (file name extension .eps .epsf .epsi) Encapsulated PostScript

EPS files are in Vector format and it allows high-resolution graphics to be produced for print. EPS files are universal and can be opened in any design editor; which is convenient for people who don’t have Adobe products.

TIFF (file name extension .tiff or .tif) Tagged Image File Format

TIFF is a raster file that can be re-sized without compromising the quality of the file. They are commonly used in desktop publishing, faxing, 3-D applications, and medical images. Designers don’t usually use these files because of their long load times.

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