There are a number of image file formats out there. You are probably familiar with gifs and jpegs, but there are also a variety of others including .eps and .tif. Graphics are broken down into two kinds of categories – vector and raster (or bitmap).
These resolution-independent images can be created with Adobe Illustrator or Macromedia Freehand & are based on mathematical equations to display their image. This means that regardless of how you resize the image, it will retain all its information. Vector files usually end with the extension “.eps”. This is the ideal format for logos.
Raster (or Bitmap) Graphics
These images are based on square bits of information called “pixels” to build the image, where each pixel is a separate color & the entire picture is made up of a patchwork of these color pieces. This means that resolution is an important in how your image will look. If the original image started out at 72 dpi at 100%, at 200%, the dpi drops to 36 dpi. If you make the image 50% of its original size, the dpi will increase to 144. Graphics with the extensions “.gif”, “.jpg”, “.tif”, and “.bmp” are among bitmap images. This format is used for images on the web, photographs, scanned images, artwork created in programs like Adobe Photoshop or MS Paint
Web Resolution vs. Print Resolution
Computer monitor only displays images at about 72 pixels/dots per inch (ppi or dpi), so you only need that resolution for web graphics. Print, however, requires a higher resolution of 300 dpi to print cleanly.
Types of Raster Graphics
- Tagged Image File Format (TIFF) – This bitmap form is the best type of image to use in print for high quality images, especially for scanned images such as photographs
- Windows Bitmap (BMP) – Another commonly used format for high quality scanned images
- JPEG – This bitmapped format is probably the most common format for receiving photographs. JPEGs use a type of built in compression to reduce file size.
NOTE: Even if the image is a tif, bmp, or a jpg, that does not necessarily mean that it is 300 dpi. If you got the jpg off the web, chances are, it’s probably only 72 dpi. Most jpgs that are 300 dpi tend to be at least over 100KB in size. BMP and TIFF files that are about 300 dpi are almost always close to 1MB or more in size.
Never Use Gifs For Print
Graphics Interchange Format (GIF) should NEVER be used in print. This format was designed specifically for on-screen viewing where quick download time was more important than quality. They are designed to display 8-bit color (256 colors) & are almost always 72 dpi or less. They will print very rough with jagged edges & nothing can be done to clean them up.