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Friday, July 18, 2014

The Difference Between Raster and Vector File

Every file saved on a computer has an extension after it.  A dot followed by letters that designate the file type.  It’s important to know the difference between some of the common file types.  With images and graphics, the most important distinction to know is the difference between Raster and Vector images. 

Raster Files or Bitmaps

Raster (or Bitmap) images are made up of pixels, dots of color that together form the image, similar to a mosaic. Photographs are always raster images, and most images you find online are likely to be raster too. Raster images will gradually lose quality as you scale them up, creating a low quality, pixelated appearance. 

The most common form of raster images is .jpg (or JPEG).  Most digital cameras will store images as jpegs by default, and most images found on the web are jpegs as well due to its small file size. 

PNGs and GIFs are similar to JPGs, but they also support transparency of an image.

Photoshop files, or PSDs, include the original layers of a Photoshop file to be edited, but can only be opened and edited with the Adobe Photoshop program.

Vector Files

Vector images do not use pixels.  Instead, they use math equations to determine how the image is formed.  Because of this, the image can be scaled up or down to any size without ever losing quality or becoming pixelated. 

EPS and PDF files are often used when saving vector images.  This is a great file type to use for large scale printing.

Two other ways to save a vector image are from the native file they’re created in .ai (an Adobe Illustrator file) and .cdr (a CorelDraw file).  These can be opened using Illustrator or CorelDraw as vector images and individual layers can be edited.

Keep in mind that these vector files can be opened with any image-viewing program, but will only remain vector images when opened with a vector-based program like Illustrator or CorelDraw.  Opening a vector image and saving it in a raster program (like the Mac’s Preview, Windows Image Viewer, or Photoshop) will rasterize the image.

When sending files to GH Imaging for printing, it is best to send files in a vector format to allow us to scale them to fit your printing surface without losing image quality.  Talk to your GH Sales Consultant for more information on file types and when to use them.
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