Magnolia Design+Communications

Sep

21

Resolving Resolution I: Vector vs. Raster

Filed Under Design Wise 

I’m sure you are familiar with the most common image file types such as JPG, TIF and even GIF. If you’re a Photoshop wiz, you’ll recognize PSD and EPS. But do you know which of these image types are Vector which are Raster images? More importantly, do you know why it’s important for you to know?

When preparing illustrations or logos for print design, use vector images, especially for large applications like signs or posters, since they are resolution independent. This simply means that these drawings are saved as mathematical equations instead of pixels, thereby making them scalable to virtually any size without distortion. It also allows these files to be used in engraving or die casting without additional billable time to modify them.

Generally, you can identify vector images by the file extensions .ai (Adobe Illustrator), .eps (Encapsulated Post Script), and .cdr (Corel Draw) just to name a few. Please note that merely saving an image as one of these file formats does not necessarily mean that the image is vector based. They would have to have been created in a vector illustration application like the ones just mentioned.

Photographs, on the other hand, are raster images, which are sometimes referred to as bitmap images. These kinds of images use individual pixels or dots of color to compose the entire image. Like your TV, the closer you zoom into the image, the more you will notice these pixels. Likewise, the more pixels you have in a given area, the more detailed the image will be and will allow you to print the image in a larger format without noticeable distortion.

This is one reason why you can’t use a low resolution photo intended for the Web for use in creating something intended to be printed, for example, a postcard. Web images, in an attempt to keep file sizes as small as possible use a standard resolution of 72ppi (pixels per inch), while the most commonly accepted resolution for print is generally 300ppi.

In Part II of this article, we’ll cover just what it means when your printer or designer talks about PPI, DPI and LPI.

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